Attack detection and prevention enables a device to detect attacks by inspecting arriving packets, and to take prevention actions to protect a private network. Prevention actions include logging, packet dropping, and blacklisting.

Attacks that the device can prevent

This section describes the attacks that the device can detect and prevent.

Single-packet attacks

Single-packet attacks are also known as malformed packet attacks. An attacker typically launches single-packet attacks by using the following methods:

· An attacker sends defective packets to a device, which causes the device to malfunction or crash.

· An attacker sends normal packets to a device, which interrupts connections or probes network topologies.

· An attacker sends a large number of forged packets to a target device, which consumes network bandwidth and causes denial of service (DoS).

Table 1 lists the single-packet attack types that the device can detect and prevent.

Table 1 Types of single-packet attacks

Single-packet attack	Description
ICMP redirect	An attacker sends ICMP redirect messages to modify the victim's routing table. The victim cannot forward packets correctly.
ICMP destination unreachable	An attacker sends ICMP destination unreachable messages to cut off the connections between the victim and its destinations.
ICMP type	A receiver responds to an ICMP packet according to its type. An attacker sends forged ICMP packets of a specific type to affect the packet processing of the victim.
ICMPv6 type	A receiver responds to an ICMPv6 packet according to its type. An attacker sends forged ICMPv6 packets of specific types to affect the packet processing of the victim.
Land	An attacker sends the victim a large number of TCP SYN packets, which contain the victim's IP address as the source and destination IP addresses. This attack exhausts the half-open connection resources on the victim, and locks the victim's system.
Large ICMP packet	An attacker sends large ICMP packets to crash the victim. Large ICMP packets can cause memory allocation error and crash the protocol stack.
Large ICMPv6 packet	An attacker sends large ICMPv6 packets to crash the victim. Large ICMPv6 packets can cause memory allocation error and crash the protocol stack.
IP options	An attacker sends IP datagrams in which the IP options are abnormal. This attack intends to probe the network topology. The target system will break down if it is incapable of processing error packets.
IP fragment	An attacker sends the victim an IP datagram with an offset smaller than 5, which causes the victim to malfunction or crash.
IP impossible packet	An attacker sends IP packets whose source IP address is the same as the destination IP address, which causes the victim to malfunction.
Tiny fragment	An attacker makes the fragment size small enough to force Layer 4 header fields into the second fragment. These fragments can pass the packet filtering because they do not hit any match.
Smurf	An attacker broadcasts an ICMP echo request to target networks. These requests contain the victim's IP address as the source IP address. Every receiver on the target networks will send an ICMP echo reply to the victim. The victim will be flooded with replies, and will be unable to provide services. Network congestion might occur.
TCP flag	An attacker sends packets with defective TCP flags to probe the operating system of the target host. Different operating systems process unconventional TCP flags differently. The target system will break down if it processes this type of packets incorrectly.
Traceroute	An attacker uses traceroute tools to probe the topology of the victim network.
WinNuke	An attacker sends Out-Of-Band (OOB) data to the TCP port 139 (NetBIOS) on the victim that runs Windows system. The malicious packets contain an illegal Urgent Pointer, which causes the victim's operating system to crash.
UDP bomb	An attacker sends a malformed UDP packet. The length value in the IP header is larger than the IP header length plus the length value in the UDP header. When the target system processes the packet, a buffer overflow can occur, which causes a system crash.
UDP Snork	An attacker sends a UDP packet with destination port 135 (the Microsoft location service) and source port 135, 7, or 19. This attack causes an NT system to exhaust its CPU.
UDP Fraggle	An attacker sends a large number of chargen packets with source UDP port 7 and destination UDP port 19 to a network. These packets use the victim's IP address as the source IP address. Replies will flood the victim, resulting in DoS.
Teardrop	An attacker sends a stream of overlapping fragments. The victim will crash when it tries to reassemble the overlapping fragments.
Ping of death	An attacker sends the victim an ICMP echo request larger than 65535 bytes that violates the IP protocol. When the victim reassembles the packet, a buffer overflow can occur, which causes a system crash.

Scanning attacks

Scanning is a preintrusion activity used to prepare for intrusion into a network. The scanning allows the attacker to find a way into the target network and to disguise the attacker's identity.

Attackers use scanning tools to probe a network, find vulnerable hosts, and discover services that are running on the hosts. Attackers can use the information to launch attacks.

The device can detect and prevent the IP sweep and port scan attacks. If an attacker performs port scanning from multiple hosts to the target host, distributed port scan attacks occur.

Flood attacks

An attacker launches a flood attack by sending a large number of forged requests to the victim in a short period of time. The victim is too busy responding to these forged requests to provide services for legal users, and a DoS attack occurs.

The device can detect and prevent the following types of flood attacks:

· SYN flood attack.

A SYN flood attacker exploits the TCP three-way handshake characteristics and makes the victim unresponsive to legal users. An attacker sends a large number of SYN packets with forged source addresses to a server. This causes the server to open a large number of half-open connections and respond to the requests. However, the server will never receive the expected ACK packets. The server is unable to accept new incoming connection requests because all of its resources are bound to half-open connections.

· ACK flood attack.

An ACK packet is a TCP packet only with the ACK flag set. Upon receiving an ACK packet from a client, the server must search half-open connections for a match.

An ACK flood attacker sends a large number of ACK packets to the server. This causes the server to be busy searching for half-open connections, and the server is unable to process packets for normal services.

· SYN-ACK flood attack.

Upon receiving a SYN-ACK packet, the server must search for the matching SYN packet it has sent. A SYN-ACK flood attacker sends a large number of SYN-ACK packets to the server. This causes the server to be busy searching for SYN packets, and the server is unable to process packets for normal services.

· FIN flood attack.

FIN packets are used to shut down TCP connections.

A FIN flood attacker sends a large number of forged FIN packets to a server. The victim might shut down correct connections, or be unable to provide services because it is busy searching for matching connections.

· RST flood attack.

RST packets are used to abort TCP connections when TCP connection errors occur.

An RST flood attacker sends a large number of forged RST packets to a server. The victim might shut down correct connections, or be unable to provide services because it is busy searching for matching connections.

· DNS flood attack.

The DNS server processes and replies all DNS queries that it receives.

A DNS flood attacker sends a large number of forged DNS queries. This attack consumes the bandwidth and resources of the DNS server, which prevents the server from processing and replying legal DNS queries.

· HTTP flood attack.

Upon receiving an HTTP GET request, the HTTP server performs complex operations, including character string searching, database traversal, data reassembly, and format switching. These operations consume a large amount of system resources.

An HTTP flood attacker sends a large number of HTTP GET requests that exceed the processing capacity of the HTTP server, which causes the server to crash.

· ICMP flood attack.

An ICMP flood attacker sends ICMP request packets, such as ping packets, to a host at a fast rate. Because the target host is busy replying to these requests, it is unable to provide services.

· ICMPv6 flood attack.

An ICMPv6 flood attacker sends ICMPv6 request packets, such as ping packets, to a host at a fast rate. Because the target host is busy replying to these requests, it is unable to provide services.

· UDP flood attack.

A UDP flood attacker sends UDP packets to a host at a fast rate. These packets consume a large amount of the target host's bandwidth, so the host cannot provide other services.

TCP fragment attack

An attacker launches TCP fragment attacks by sending attack TCP fragments defined in RFC 1858:

· First fragments in which the TCP header is smaller than 20 bytes.

· Non-first fragments with a fragment offset of 8 bytes (FO=1).

Typically, packet filter detects the source and destination IP addresses, source and destination ports, and transport layer protocol of the first fragment of a TCP packet. If the first fragment passes the detection, all subsequent fragments of the TCP packet are allowed to pass through.

Because the first fragment of attack TCP packets does not hit any match in the packet filter, the subsequent fragments can all pass through. After the receiving host reassembles the fragments, a TCP fragment attack occurs.

To prevent TCP fragment attacks, enable TCP fragment attack prevention to drop attack TCP fragments.

Login DoS attack

In a login DoS attack, a malicious user can attempt to interfere with the normal operations of a device by flooding it with login requests. These requests consume the authentication resources, which makes the device unable to allow legal users to log in.

You can configure login attack prevention to prevent the login DoS attacks. This feature blocks user login attempts for a period of time after the user fails the maximum number of successive login attempts.

Login dictionary attack

The login dictionary attack is an automated process to attempt to log in by trying all possible passwords from a pre-arranged list of values (the dictionary). Multiple login attempts can occur in a short period of time.

You can configure the login delay feature to slow down the login dictionary attacks. This feature enables the device to delay accepting another login request after detecting a failed login attempt for a user.

Blacklist feature

The IP blacklist feature is an attack prevention method that filters packets by source IP addresses in blacklist entries. Compared with ACL-based packet filtering, IP blacklist filtering is simpler and provides effective screening at a faster speed.

Attack detection and prevention configuration task list

Tasks at a glance
(Required.) Configuring an attack defense policy: · (Required.) Creating an attack defense policy · (Required.) Perform at least one of the following tasks to configure attack detection: ¡ Configuring a single-packet attack defense policy ¡ Configuring a scanning attack defense policy ¡ Configuring a flood attack defense policy · (Optional.) Configuring attack detection exemption
(Required.) Perform at least one of the tasks to apply an attack defense policy: · Applying an attack defense policy to an interface · Applying an attack defense policy to the device
(Optional.) Enabling log non-aggregation for single-packet attack events
(Optional.) Configuring TCP fragment attack prevention
(Optional.) Configuring the IP blacklist feature
(Optional.) Configuring login attack prevention
(Optional.) Enabling the login delay

Configuring an attack defense policy

Creating an attack defense policy

An attack defense policy can contain a set of attack detection and prevention configuration against multiple attacks.

To create an attack defense policy:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Create an attack defense policy and enter its view.	attack-defense policy policy-name	By default, no attack defense policy exists.

Configuring a single-packet attack defense policy

Apply the single-packet attack defense policy to the interface that is connected to the external network.

Single-packet attack detection inspects incoming packets based on the packet signature. If an attack packet is detected, the device can take the following actions:

· Output logs (the default action).

· Drop attack packets.

You can also configure the device to not take any actions.

To configure a single-packet attack defense policy:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Configure signature detection for single-packet attacks.	· signature detect { fraggle \| fragment \| impossible \| land \| large-icmp \| large-icmpv6 \| smurf \| snork \| tcp-all-flags \| tcp-fin-only \| tcp-invalid-flags \| tcp-null-flag \| tcp-syn-fin \| tiny-fragment \| traceroute \| udp-bomb \| winnuke } [ action { { drop \| logging } * \| none } ] · signature detect { ip-option-abnormal \| ping-of-death \| teardrop } action { drop \| logging } * · signature detect icmp-type { icmp-type-value \| address-mask-reply \| address-mask-request \| destination-unreachable \| echo-reply \| echo-request \| information-reply \| information-request \| parameter-problem \| redirect \| source-quench \| time-exceeded \| timestamp-reply \| timestamp-request } [ action { { drop \| logging } * \| none } ] · signature detect icmpv6-type { icmpv6-type-value \| destination-unreachable \| echo-reply \| echo-request \| group-query \| group-reduction \| group-report \| packet-too-big \| parameter-problem \| time-exceeded } [ action { { drop \| logging } * \| none } ] · signature detect ip-option { option-code \| internet-timestamp \| loose-source-routing \| record-route \| route-alert \| security \| stream-id \| strict-source-routing } [ action { { drop \| logging } * \| none } ] · signature detect ipv6-ext-header ext-header-value [ action { { drop \| logging } * \| none } ]	By default, signature detection is not configured for single-packet attacks. You can configure signature detection for multiple single-packet attacks.
4. (Optional.) Set the maximum length of safe ICMP or ICMPv6 packets.	signature { large-icmp \| large-icmpv6 } max-length length	By default, the maximum length of safe ICMP or ICMPv6 packets is 4000 bytes. A large ICMP or ICMPv6 attack occurs if an ICMP or ICMPv6 packet larger than the specified length is detected.
5. (Optional.) Specify the actions against single-packet attacks of a specific level.	signature level { high \| info \| low \| medium } action { { drop \| logging } * \| none }	The default action is logging for single-packet attacks of the informational and low levels. The default actions are logging and drop for single-packet attacks of the medium and high levels.
6. (Optional.) Enable signature detection for single-packet attacks of a specific level.	signature level { high \| info \| low \| medium } detect	By default, signature detection is disabled for all levels of single-packet attacks.

Configuring a scanning attack defense policy

Apply a scanning attack defense policy to the interface that is connected to the external network.

Scanning attack detection inspects the incoming packet rate of connections to the target system. If a source initiates connections at a rate equal to or exceeding the pre-defined threshold, the device can take the following actions:

· Output logs.

· Drop subsequent packets from the IP address of the attacker.

· Add the attacker's IP address to the IP blacklist.

To blacklist the attackers, you must enable the blacklist feature globally or on the interface where the defense policy is applied. For more information about the blacklist, see "Configuring the IP blacklist feature."

To configure a scanning attack defense policy:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Configure scanning attack detection.	scan detect level { high \| low \| medium } action { { block-source [ timeout minutes ] \| drop } \| logging } *	By default, scanning attack detection is not configured.

Configuring a flood attack defense policy

Apply a flood attack defense policy to the interface that is connected to the external network to protect internal servers.

Flood attack detection monitors the rate at which connections are initiated to the internal servers.

With flood attack detection enabled, the device is in attack detection state. When the packet sending rate to an IP address reaches the threshold, the device enters prevention state and takes the specified actions. When the rate is below the silence threshold (three-fourths of the threshold), the device returns to the attack detection state.

If a device has multiple service cards, the global trigger threshold you set takes effect on each service card. The global trigger threshold of the device is the product of multiplying the value you set by the service card quantity.

You can configure flood attack detection and prevention for a specific IP address. For non-specific IP addresses, the device uses the global attack prevention settings.

Configuring a SYN flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global SYN flood attack detection.	syn-flood detect non-specific	By default, global SYN flood attack detection is disabled.
4. Set the global trigger threshold for SYN flood attack prevention.	syn-flood threshold threshold-value	The default setting is 1000.
5. Specify global actions against SYN flood attacks.	syn-flood action { drop \| logging } *	By default, no global action is specified for SYN flood attacks.
6. Configure IP address-specific SYN flood attack detection.	syn-flood detect { ip ipv4-address \| ipv6 ipv6-address } [ vpn-instance vpn-instance-name ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific SYN flood attack detection is not configured.

Configuring an ACK flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global ACK flood attack detection.	ack-flood detect non-specific	By default, global ACK flood attack detection is disabled.
4. Set the global trigger threshold for ACK flood attack prevention.	ack-flood threshold threshold-value	The default setting is 1000.
5. Specify global actions against ACK flood attacks.	ack-flood action { drop \| logging } *	By default, no global action is specified for ACK flood attacks.
6. Configure IP address-specific ACK flood attack detection.	ack-flood detect { ip ipv4-address \| ipv6 ipv6-address } [ vpn-instance vpn-instance-name ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific ACK flood attack detection is not configured.

Configuring a SYN-ACK flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global SYN-ACK flood attack detection.	syn-ack-flood detect non-specific	By default, global SYN-ACK flood attack detection is disabled.
4. Set the global trigger threshold for SYN-ACK flood attack prevention.	syn-ack-flood threshold threshold-value	The default setting is 1000.
5. Specify global actions against SYN-ACK flood attacks.	syn-ack-flood action { drop \| logging } *	By default, no global action is specified for SYN-ACK flood attacks.
6. Configure IP address-specific SYN-ACK flood attack detection.	syn-ack-flood detect { ip ipv4-address \| ipv6 ipv6-address } [ vpn-instance vpn-instance-name ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific SYN-ACK flood attack detection is not configured.

Configuring a FIN flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global FIN flood attack detection.	fin-flood detect non-specific	By default, global FIN flood attack detection is disabled.
4. Set the global trigger threshold for FIN flood attack prevention.	fin-flood threshold threshold-value	The default setting is 1000.
5. Specify global actions against FIN flood attacks.	fin-flood action { drop \| logging } *	By default, no global action is specified for FIN flood attacks.
6. Configure IP address-specific FIN flood attack detection.	fin-flood detect { ip ipv4-address \| ipv6 ipv6-address } [ vpn-instance vpn-instance-name ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific FIN flood attack detection is not configured.

Configuring an RST flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global RST flood attack detection.	rst-flood detect non-specific	By default, global RST flood attack detection is disabled.
4. Set the global trigger threshold for RST flood attack prevention.	rst-flood threshold threshold-value	The default setting is 1000.
5. Specify global actions against RST flood attacks.	rst-flood action { drop \| logging } *	By default, no global action is specified for RST flood attacks.
6. Configure IP address-specific RST flood attack detection.	rst-flood detect { ip ipv4-address \| ipv6 ipv6-address } [ vpn-instance vpn-instance-name ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific RST flood attack detection is not configured.

Configuring an ICMP flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global ICMP flood attack detection.	icmp-flood detect non-specific	By default, global ICMP flood attack detection is disabled.
4. Set the global trigger threshold for ICMP flood attack prevention.	icmp-flood threshold threshold-value	The default setting is 1000.
5. Specify global actions against ICMP flood attacks.	icmp-flood action { drop \| logging } *	By default, no global action is specified for ICMP flood attacks.
6. Configure IP address-specific ICMP flood attack detection.	icmp-flood detect ip ip-address [ vpn-instance vpn-instance-name ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific ICMP flood attack detection is not configured.

Configuring an ICMPv6 flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global ICMPv6 flood attack detection.	icmpv6-flood detect non-specific	By default, global ICMPv6 flood attack detection is disabled.
4. Set the global trigger threshold for ICMPv6 flood attack prevention.	icmpv6-flood threshold threshold-value	The default setting is 1000.
5. Specify global actions against ICMPv6 flood attacks.	icmpv6-flood action { drop \| logging } *	By default, no global action is specified for ICMPv6 flood attacks.
6. Configure IP address-specific ICMPv6 flood attack detection.	icmpv6-flood detect ipv6 ipv6-address [ vpn-instance vpn-instance-name ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific ICMPv6 flood attack detection is not configured.

Configuring a UDP flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global UDP flood attack detection.	udp-flood detect non-specific	By default, global UDP flood attack detection is disabled.
4. Set the global trigger threshold for UDP flood attack prevention.	udp-flood threshold threshold-value	The default setting is 1000.
5. Specify global actions against UDP flood attacks.	udp-flood action { drop \| logging } *	By default, no global action is specified for UDP flood attacks.
6. Configure IP address-specific UDP flood attack detection.	udp-flood detect { ip ipv4-address \| ipv6 ipv6-address } [ vpn-instance vpn-instance-name ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific UDP flood attack detection is not configured.

Configuring a DNS flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global DNS flood attack detection.	dns-flood detect non-specific	By default, global DNS flood attack detection is disabled.
4. Set the global trigger threshold for DNS flood attack prevention.	dns-flood threshold threshold-value	The default setting is 1000.
5. (Optional.) Specify the global ports to be protected against DNS flood attacks.	dns-flood port port-list	By default, DNS flood attack prevention protects port 53.
6. Specify global actions against DNS flood attacks.	dns-flood action { drop \| logging } *	By default, no global action is specified for DNS flood attacks.
7. Configure IP address-specific DNS flood attack detection.	dns-flood detect { ip ipv4-address \| ipv6 ipv6-address } [ vpn-instance vpn-instance-name ] [ port port-list ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific DNS flood attack detection is not configured.

Configuring an HTTP flood attack defense policy

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Enable global HTTP flood attack detection.	http-flood detect non-specific	By default, global HTTP flood attack detection is disabled.
4. Set the global trigger threshold for HTTP flood attack prevention.	http-flood threshold threshold-value	The default setting is 1000.
5. (Optional.) Specify the global ports to be protected against HTTP flood attacks.	http-flood port port-list	By default, HTTP flood attack prevention protects port 80.
6. Specify global actions against HTTP flood attacks.	http-flood action { drop \| logging } *	By default, no global action is specified for HTTP flood attacks.
7. Configure IP address-specific HTTP flood attack detection.	http-flood detect { ip ipv4-address \| ipv6 ipv6-address } [ vpn-instance vpn-instance-name ] [ port port-list ] [ threshold threshold-value ] [ action { { drop \| logging } * \| none } ]	By default, IP address-specific HTTP flood attack detection is not configured.

Configuring attack detection exemption

The attack defense policy uses the ACL to identify exempted packets. The policy does not check the packets permitted by the ACL. You can configure the ACL to identify packets from trusted servers. The exemption feature reduces the false alarm rate and improves packet processing efficiency. For example, the attack defense policy identifies multicast packets with the same source addresses and different destination addresses as scanning attack packets (for example, OSPF or PIM packets). You can configure an ACL to exempt such packets from attack detection.

If an ACL is used for attack detection exemption, only the following match criteria in the ACL permit rules take effect:

· Source IP address.

· Destination IP address.

· Source port.

· Destination port.

· Protocol.

· L3VPN instance.

· The fragment keyword for matching non-first fragments.

To configure attack detection exemption:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter attack defense policy view.	attack-defense policy policy-name	N/A
3. Configure attack detection exemption.	exempt acl [ ipv6 ] { acl-number \| name acl-name }	By default, attack detection exemption is not configured.

Applying an attack defense policy to an interface

An attack defense policy does not take effect unless you apply it to an interface.

To apply an attack defense policy to an interface:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter system view.	interface interface-type interface-number	N/A
3. Apply an attack defense policy to the interface.	attack-defense apply policy policy-name	By default, no attack defense policy is applied to the interface.

Applying an attack defense policy to the device

An attack defense policy applied to the device itself rather than the interfaces detects packets destined for the device and prevents attacks targeted at the device.

The device uses hardware to implement packet forwarding and uses software to process packets if the packets are destined for the device. The software does not provide any attack defense features, so you must apply an attack defense policy to the device to prevent attacks aimed at the device.

If a device and its interfaces have attack defense policies applied, a packet destined for the device is processed as follows:

1. The policy applied to the receiving interface processes the packet.

2. If the packet is not dropped by the receiving interface, the policy applied to the device processes the packet.

To apply an attack defense policy to the device:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Apply an attack defense policy to the device.	attack-defense local apply policy policy-name	By default, no attack defense policy is applied to the device.

Enabling log non-aggregation for single-packet attack events

Log aggregation aggregates multiple logs generated during a period of time and sends one log. Logs that are aggregated must have the following attributes in common:

· Attacks are detected on the same interface or destined for the device.

· Attack type.

· Attack defense action.

· Source and destination IP addresses.

· VPN instance to which the victim IP address belongs.

As a best practice, do not disable log aggregation. A large number of logs will consume the display resources of the console.

To enable log non-aggregation for single-packet attack events:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable log non-aggregation for single-packet attack events.	attack-defense signature log non-aggregate	By default, log non-aggregation is disabled for single-packet attack events.

Configuring TCP fragment attack prevention

The TCP fragment attack prevention feature detects the length and fragment offset of received TCP fragments and drops attack TCP fragments.

TCP fragment attack prevention takes precedence over single-packet attack prevention. When both are used, incoming TCP packets are processed first by TCP fragment attack prevention and then by the single-packet attack defense policy.

To configure TCP fragment attack prevention:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable TCP fragment attack prevention.	attack-defense tcp fragment enable	By default, TCP fragment attack prevention is enabled. TCP fragment attack prevention is typically used alone.

Step

Command

Remarks

1. Enter system view.

system-view

N/A

2. Enable TCP fragment attack prevention.

attack-defense tcp fragment enable

By default, TCP fragment attack prevention is enabled.

TCP fragment attack prevention is typically used alone.

Configuring the IP blacklist feature

The IP blacklist feature filters packets sourced from IP addresses in blacklist entries.

IP blacklist entries can be manually added or dynamically learned:

· You can manually add an IP blacklist entry. These entries do not age out by default. You can set an aging time for each entry.

· The device can automatically add IP blacklist entries when collaborating with scanning attack detection. Each dynamically learned IP blacklist entry has an aging time, which is user configurable. Make sure the block-source keyword is specified as the scanning attack prevention action. For more information about the scanning attack detection and prevention, see "Configuring a scanning attack defense policy."

To configure the IP blacklist feature:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. (Optional.) Enable the global blacklist feature.	blacklist global enable	By default, the global blacklist feature is disabled. If the global blacklist feature is enabled, the blacklist feature is enabled on all interfaces.
3. (Optional.) Add an IPv4 blacklist entry.	blacklist ip source-ip-address [ vpn-instance vpn-instance-name ] [ timeout minutes ]	By default, no IPv4 blacklist entries exist.
4. (Optional.) Add an IPv6 blacklist entry.	blacklist ipv6 source-ipv6-address [ vpn-instance vpn-instance-name ] [ timeout minutes ]	By default, no IPv6 blacklist entries exist.
5. (Optional.) Enable logging for the blacklist feature.	blacklist logging enable	By default, logging is disabled for the blacklist feature.

Configuring login attack prevention

The login attack prevention feature detects a login DoS attack if a user fails the maximum number of successive login attempts. The feature triggers the blacklist feature to add the user's IP to the blacklist. Following login attempts from the user is blocked for the block period. For login attack prevention to take effect, you must enable the global blacklist feature.

This feature can effectively prevent login DoS attacks.

To configure login attack prevention:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable login attack prevention.	attack-defense login enable	By default, login attack prevention is disabled.
3. Set the maximum number of successive login failures.	attack-defense login max-attempt max-attempt	The default value is three.
4. Set the block period during which a login attempt is blocked.	attack-defense login block-timeout minutes	The default value is 60 minutes.
5. Enable the global blacklist feature.	blacklist global enable	By default, the global blacklist feature is disabled.

Enabling the login delay

The login delay feature delays the device from accepting a login request from a user after the user fails a login attempt. This feature can slow down login dictionary attacks.

The login delay feature is independent of the login attack prevention feature.

To enable the login delay:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable the login delay feature.	attack-defense login reauthentication-delay seconds	By default, the login delay feature is disabled. The device does not delay accepting a login request from a user who has failed a login attempt.

Displaying and maintaining attack detection and prevention

Use the display commands in any view and the reset commands in user view.

To display and maintain attack detection and prevention:

Task	Command
(In standalone mode.) Display attack detection and prevention statistics on an interface.	display attack-defense statistics interface interface-type interface-number [ slot slot-number ]
(In IRF mode.) Display attack detection and prevention statistics on an interface.	display attack-defense statistics interface interface-type interface-number [ chassis chassis-number slot slot-number ]
(In standalone mode.) Display attack detection and prevention statistics for the device.	display attack-defense statistics local [ slot slot-number ]
(In IRF mode.) Display attack detection and prevention statistics for the device.	display attack-defense statistics local [ chassis chassis-number slot slot-number ]
Display attack defense policy configuration.	display attack-defense policy [ policy-name ]
(In standalone mode.) Display information about IPv4 scanning attackers.	display attack-defense scan attacker ip [ interface interface-type interface-number [ slot slot-number ] \| [ local ] [ slot slot-number ] ] [ count ]
(In IRF mode.) Display information about IPv4 scanning attackers.	display attack-defense scan attacker ip [ interface interface-type interface-number [ chassis chassis-number slot slot-number ] \| [ local ] [ chassis chassis-number slot slot-number ] ] [ count ]
(In standalone mode.) Display information about IPv6 scanning attackers.	display attack-defense scan attacker ipv6 [ interface interface-type interface-number [ slot slot-number ] \| [ local ] [ slot slot-number ] ] [ count ]
(In IRF mode.) Display information about IPv6 scanning attackers.	display attack-defense scan attacker ipv6 [ interface interface-type interface-number [ chassis chassis-number slot slot-number ] \| [ local ] [ chassis chassis-number slot slot-number ] ] [ count ]
(In standalone mode.) Display information about IPv4 scanning attack victims.	display attack-defense scan victim ip [ interface interface-type interface-number [ slot slot-number ] \| [ local ] [ slot slot-number ] ] [ count ]
(In IRF mode.) Display information about IPv4 scanning attack victims.	display attack-defense scan victim ip [ interface interface-type interface-number [ chassis chassis-number slot slot-number ] \| [ local ] [ chassis chassis-number slot slot-number ] ] [ count ]
(In standalone mode.) Display information about IPv6 scanning attack victims.	display attack-defense scan victim ipv6 [ interface interface-type interface-number [ slot slot-number ] \| [ local ] [ slot slot-number ] ] [ count ]
(In IRF mode.) Display information about IPv6 scanning attack victims.	display attack-defense scan victim ipv6 [ interface interface-type interface-number [ chassis chassis-number slot slot-number ] \| [ local ] [ chassis chassis-number slot slot-number ] ] [ count ]
(In standalone mode.) Display flood attack detection and prevention statistics for an IPv4 address.	display attack-defense { ack-flood \| dns-flood \| fin-flood \| flood \| http-flood \| icmp-flood \| rst-flood \| syn-ack-flood \| syn-flood \| udp-flood } statistics ip [ ip-address [ vpn vpn-instance-name ] ] [ interface interface-type interface-number [ slot slot-number ] \| [ local ] [ slot slot-number ] ] [ count ]
(In IRF mode.) Display flood attack detection and prevention statistics for an IPv4 address.	display attack-defense { ack-flood \| dns-flood \| fin-flood \| flood \| http-flood \| icmp-flood \| rst-flood \| syn-ack-flood \| syn-flood \| udp-flood } statistics ip [ ip-address [ vpn vpn-instance-name ] ] [ interface interface-type interface-number [ chassis chassis-number slot slot-number ] \| [ local ] [ chassis chassis-number slot slot-number ] ] [ count ]
(In standalone mode.) Display flood attack detection and prevention statistics for an IPv6 address.	display attack-defense { ack-flood \| dns-flood \| fin-flood \| flood \| http-flood \| icmpv6-flood \| rst-flood \| syn-ack-flood \| syn-flood \| udp-flood } statistics ipv6 [ ipv6-address [ vpn vpn-instance-name ] ] [ interface interface-type interface-number [ slot slot-number ] \| [ local ] [ slot slot-number ] ] [ count ]
(In IRF mode.) Display flood attack detection and prevention statistics for an IPv6 address.	display attack-defense { ack-flood \| dns-flood \| fin-flood \| flood \| http-flood \| icmpv6-flood \| rst-flood \| syn-ack-flood \| syn-flood \| udp-flood } statistics ipv6 [ ipv6-address [ vpn vpn-instance-name ] ] [ interface interface-type interface-number [ chassis chassis-number slot slot-number ] \| [ local ] [ chassis chassis-number slot slot-number ] ] [ count ]
(In standalone mode.) Display information about IPv4 addresses protected by flood attack detection and prevention.	display attack-defense policy policy-name { ack-flood \| dns-flood \| fin-flood \| flood \| http-flood \| icmp-flood \| rst-flood \| syn-ack-flood \| syn-flood \| udp-flood } ip [ ip-address [ vpn vpn-instance-name ] ] [ slot slot-number ] [ count ]
(In IRF mode.) Display information about IPv4 addresses protected by flood attack detection and prevention.	display attack-defense policy policy-name { ack-flood \| dns-flood \| fin-flood \| flood \| http-flood \| icmp-flood \| rst-flood \| syn-ack-flood \| syn-flood \| udp-flood } ip [ ip-address [ vpn vpn-instance-name ] ] [ chassis chassis-number slot slot-number ] [ count ]
(In standalone mode.) Display information about IPv6 addresses protected by flood attack detection and prevention.	display attack-defense policy policy-name { ack-flood \| dns-flood \| fin-flood \| flood \| http-flood \| icmpv6-flood \| rst-flood \| syn-ack-flood \| syn-flood \| udp-flood } ipv6 [ ipv6-address [ vpn vpn-instance-name ] ] [ slot slot-number ] [ count ]
(In IRF mode.) Display information about IPv6 addresses protected by flood attack detection and prevention.	display attack-defense policy policy-name { ack-flood \| dns-flood \| fin-flood \| flood \| http-flood \| icmpv6-flood \| rst-flood \| syn-ack-flood \| syn-flood \| udp-flood } ipv6 [ ipv6-address [ vpn vpn-instance-name ] ] [ chassis chassis-number slot slot-number ] [ count ]
Display IPv4 blacklist entries.	display blacklist ip [ source-ip-address [ vpn-instance vpn-instance-name ] ] [ count ]
Display IPv6 blacklist entries.	display blacklist ipv6 [ source-ipv6-address [ vpn-instance vpn-instance-name ] ] [ count ]
Clear attack detection and prevention statistics for an interface.	reset attack-defense statistics interface interface-type interface-number
Clear attack detection and prevention statistics for the device.	reset attack-defense statistics local
Clear flood attack detection and prevention statistics.	reset attack-defense policy policy-name flood protected { ip \| ipv6 } statistics
Clear dynamic IPv4 blacklist entries.	reset blacklist ip { source-ip-address [ vpn-instance vpn-instance-name ] \| all }
Clear dynamic IPv6 blacklist entries.	reset blacklist ipv6 { source-ipv6-address [ vpn-instance vpn-instance-name ] \| all }
Clear blacklist statistics.	reset blacklist statistics

Attack detection and prevention configuration examples

Interface-based attack detection and prevention configuration example

Network requirements

As shown in Figure 1, the device is the gateway for the internal network.

Configure an attack defense policy and apply the policy to VLAN-interface 3 to meet the following requirements:

· Provide low-level scanning attack detection for internal hosts and servers. If a scanning attack is detected, log the attack and keep the attacker on the blacklist for 10 minutes.

· Protect internal hosts and servers against smurf attacks. If a smurf attack is detected, log the attack.

· Protect the internal server against SYN flood attacks. If the number of SYN packets sent to the server per second reaches or exceeds 5000, log the attack and drop subsequent packets.

Figure 1 Network diagram

Configuration procedure

# Configure IP addresses for the interfaces on the device. (Details not shown.)

# Enable the global blacklist feature.

<Device> system-view

[Device] blacklist global enable

# Create attack defense policy a1.

[Device] attack-defense policy a1

# Configure signature detection for smurf attacks, and specify logging as the prevention action.

[Device-attack-defense-policy-a1] signature detect smurf action logging

# Configure low-level scanning attack detection, specify logging and block-source as the prevention actions, and set the blacklist entry aging time to 10 minutes.

[Device-attack-defense-policy-a1] scan detect level low action logging block-source timeout 10

# Configure SYN flood attack detection for 10.1.1.2, set the attack prevention triggering threshold to 5000, and specify logging and drop as the prevention actions.

[Device-attack-defense-policy-a1] syn-flood detect ip 10.1.1.2 threshold 5000 action logging drop

[Device-attack-defense-policy-a1] quit

# Apply attack defense policy a1 to VLAN-interface 3.

[Device] interface vlan-interface 3

[Device-Vlan-interface3] attack-defense apply policy a1

[Device-Vlan-interface3] quit

Verifying the configuration

# Verify that attack defense policy a1 is successfully configured.

[Device] display attack-defense policy a1

Attack-defense Policy Information

--------------------------------------------------------------------------

Policy name : a1

Applied list : Vlan3

--------------------------------------------------------------------------

Exempt IPv4 ACL : Not configured

Exempt IPv6 ACL : Not configured

--------------------------------------------------------------------------

Actions: BS-Block source L-Logging D-Drop N-None

Signature attack defense configuration:

Signature name Defense Level Actions

Fragment Disabled low L

Impossible Disabled medium L,D

Teardrop Disabled medium L,D

Tiny fragment Disabled low L

IP option abnormal Disabled medium L,D

Smurf Enabled medium L

Traceroute Disabled low L

Ping of death Disabled medium L,D

Large ICMP Disabled info L

Max length 4000 bytes

Large ICMPv6 Disabled info L

Max length 4000 bytes

TCP invalid flags Disabled medium L,D

TCP null flag Disabled medium L,D

TCP all flags Disabled medium L,D

TCP SYN-FIN flags Disabled medium L,D

TCP FIN only flag Disabled medium L,D

TCP Land Disabled medium L,D

Winnuke Disabled medium L,D

UDP Bomb Disabled medium L,D

UDP Snork Disabled medium L,D

UDP Fraggle Disabled medium L,D

IP option record route Disabled info L

IP option internet timestamp Disabled info L

IP option security Disabled info L

IP option loose source routing Disabled info L

IP option stream ID Disabled info L

IP option strict source routing Disabled info L

IP option route alert Disabled info L

ICMP echo request Disabled info L

ICMP echo reply Disabled info L

ICMP source quench Disabled info L

ICMP destination unreachable Disabled info L

ICMP redirect Disabled info L

ICMP time exceeded Disabled info L

ICMP parameter problem Disabled info L

ICMP timestamp request Disabled info L

ICMP timestamp reply Disabled info L

ICMP information request Disabled info L

ICMP information reply Disabled info L

ICMP address mask request Disabled info L

ICMP address mask reply Disabled info L

ICMPv6 echo request Disabled info L

ICMPv6 echo reply Disabled info L

ICMPv6 group membership query Disabled info L

ICMPv6 group membership report Disabled info L

ICMPv6 group membership reduction Disabled info L

ICMPv6 destination unreachable Disabled info L

ICMPv6 time exceeded Disabled info L

ICMPv6 parameter problem Disabled info L

ICMPv6 packet too big Disabled info L

Scan attack defense configuration:

Defense : Enabled

Level : low

Actions : L,BS(10)

Flood attack defense configuration:

Flood type Global thres(pps) Global actions Service ports Non-specific

SYN flood 1000(default) - - Disabled

ACK flood 1000(default) - - Disabled

SYN-ACK flood 1000(default) - - Disabled

RST flood 1000(default) - - Disabled

FIN flood 1000(default) - - Disabled

UDP flood 1000(default) - - Disabled

ICMP flood 1000(default) - - Disabled

ICMPv6 flood 1000(default) - - Disabled

DNS flood 1000(default) - 53 Disabled

HTTP flood 1000(default) - 80 Disabled

Flood attack defense for protected IP addresses:

Address VPN instance Flood type Thres(pps) Actions Ports

10.1.1.2 -- SYN-FLOOD 5000 L,D -

# Verify that the attack detection and prevention takes effect on VLAN-interface 3.

[Device] display attack-defense statistics interface Vlan-interface 3

Attack policy name: a1

Scan attack defense statistics:

AttackType AttackTimes Dropped

Port scan 2 0

IP sweep 3 0

Distribute port scan 1 0

Flood attack defense statistics:

AttackType AttackTimes Dropped

No flood attacks detected.

Signature attack defense statistics:

AttackType AttackTimes Dropped

Smurf 1 0

# Verify that the IPv4 blacklist feature collaborates with the scanning attack detection.

[Device] display blacklist ip

IP address VPN instance DS-Lite tunnel peer Type TTL(sec) Dropped

5.5.5.5 -- -- Dynamic 600 353452

IP blacklist configuration example

Network requirements

As shown in Figure 2, configure the IP blacklist feature on the device to block packets from the attacker Host D permanently and from Host C for 50 minutes.

Figure 2 Network diagram

Configuration procedure

# Configure IP addresses for the interfaces on the device. (Details not shown.)

# Enable the global blacklist feature.

<Device> system-view

[Device] blacklist global enable

# Add an IPv4 blacklist entry for Host D.

[Device] blacklist ip 5.5.5.5

# Add an IPv4 blacklist entry for Host C and set the blacklist entry aging time to 50 minutes.

[Device] blacklist ip 192.168.1.4 timeout 50

Verifying the configuration

# Verify that the IPv4 blacklist entries are successfully added.

<Device> display blacklist ip

IP address VPN instance DS-Lite tunnel peer Type TTL(sec) Dropped

5.5.5.5 -- -- Manual Never 0

192.168.1.4 -- -- Manual 2989 0

# Verify that the device drops packets from Host D. (Details not shown.)

# Execute the undo blacklist ip 5.5.5.5 command and verify that the device forwards packets from Host D. (Details not shown.)

# Verify that the device drops packets from Host C for 50 minutes and forwards packets from Host C after 50 minutes. (Details not shown.)

10-Security Configuration Guide

Configuring attack detection and prevention

Attacks that the device can prevent

Attack detection and prevention configuration task list

Creating an attack defense policy

Configuring a single-packet attack defense policy

Configuring a SYN flood attack defense policy

Configuring an ACK flood attack defense policy

Configuring a SYN-ACK flood attack defense policy

Configuring a FIN flood attack defense policy

Configuring an RST flood attack defense policy

Configuring an ICMP flood attack defense policy

Configuring an ICMPv6 flood attack defense policy

Configuring a UDP flood attack defense policy

Displaying and maintaining attack detection and prevention

Network requirements

Configuration procedure

Verifying the configuration

IP blacklist configuration example

Network requirements

Configuration procedure

Verifying the configuration

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