Contents

Configuring attack detection and prevention· 1

About attack detection and prevention· 1

Attacks that the device can prevent 1

Single-packet attacks· 1

Scanning attacks· 2

Flood attacks· 3

TCP fragment attack· 4

Login DoS attack· 4

Login dictionary attack· 4

Attack detection and prevention tasks at a glance· 5

Configuring and applying an attack defense policy· 5

Creating an attack defense policy· 5

Configuring a single-packet attack defense policy· 6

Configuring a scanning attack defense policy· 7

Configuring a flood attack defense policy· 7

Configuring attack detection exemption· 12

Applying an attack defense policy to an interface· 13

Applying an attack defense policy to the device· 13

Enabling log non-aggregation for single-packet attack events· 14

Configuring TCP fragment attack prevention· 14

Enabling the login delay· 15

Verifying and maintaining attack detection and prevention· 15

Verifying attack defense configuration· 15

Displaying attack detection and prevention entries· 15

Displaying and clearing attack detection and prevention statistics· 16

Attack detection and prevention configuration examples· 17

Example: Configuring interface-based attack detection and prevention· 17

 

Configuring attack detection and prevention

About attack detection and prevention

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 and packet dropping.

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 no larger 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 packets with source UDP port 7 and destination UDP port 19 (UDP chargen port) 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.
IPv6 extension header	An attack sends the victim a packet with an irregular number of IPv6 extension headers. Resolving this packet is resource consuming and degrades the forwarding performance.

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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 or POST 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 or POST 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.

Attack detection and prevention tasks at a glance

To configure attack detection and prevention, perform the following tasks:

1.     Configuring and applying an attack defense policy

a.     Creating an attack defense policy

b.     Configuring an attack defense policy

Choose the following tasks as needed:

-     Configuring a single-packet attack defense policy

-     Configuring a scanning attack defense policy

-     Configuring a flood attack defense policy

c.     (Optional.) Configuring attack detection exemption

d.     Applying an attack defense policy

Choose the following tasks as needed:

-     Applying an attack defense policy to an interface

-     Applying an attack defense policy to the device

2.     (Optional.) Enabling log non-aggregation for single-packet attack events

3.     (Optional.) Configuring TCP fragment attack prevention

Typically, this feature is separately used.

4.     (Optional.) Enabling the login delay

Configuring and applying an attack defense policy

Creating an attack defense policy

About this task

An attack defense policy contains a set of attack detection and prevention configuration.

To configure attack defense configuration such as detection signatures and protection actions, you must first create an attack defense policy and enter its view.

Restrictions and guidelines

CAUTION: The default thresholds for triggering attack prevention might not be appropriate for your network. Set appropriate according to the actual application scenarios. Small thresholds might affect the Internet or webpage access speed. Large thresholds might make your network vulnerable to attacks.

 

Procedure

1.     Enter system view.

system-view

2.     Create an attack defense policy and enter its view.

attack-defense policy policy-name

Configuring a single-packet attack defense policy

About this task

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.

Procedure

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

3.     Configure signature detection for specific single-packet attack types, and specify the actions against the attacks.

¡     Configure signature detection for well-known single-packet attacks, and specify the actions against the 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 } *

¡     Configure signature detection for ICMP packet attacks, and specify the actions against the attacks.

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 } ]

¡     Configure signature detection for ICMPv6 packet attacks, and specify the actions against the attacks.

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 } ]

¡     Configure signature detection for IP option attacks, and specify the actions against the attacks.

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 } ]

¡     Configure signature detection for IP abnormal option attacks, and specify the actions against the attacks.

signature detect ipv6-ext-header-abnormal [ action { { drop | logging } * | none } ]

By default, signature detection is not configured for 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.

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

About this task

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.

If logging is specified for IP sweep and port scan attacks, the system outputs logs for only IP sweep attacks when both the IP sweep and port scan attack thresholds are reached.

Procedure

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

3.     Configure scanning attack detection.

scan detect level { { high | low | medium } | user-defined { port-scan-threshold threshold-value | ip-sweep-threshold threshold-value } * [ period period-value ] } action { drop | logging } *

By default, scanning attack detection is not configured.

Configuring a flood attack defense policy

About this task

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.

Restrictions and guidelines for flood attack detection and prevention

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

About this task

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.

Restrictions and guidelines

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.

Procedure

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

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

1.     Enter system view.

system-view

2.     Enter system view.

interface interface-type interface-number

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.

4.     Specify a traffic processing slot for the interface.

service slot slot-number

By default, no traffic processing slot is specified for an interface. Traffic on an interface is processed on the slot at which the traffic arrives.

If you apply an attack defense policy to a global interface, specify a traffic processing slot for the interface. If you do not specify a traffic processing slot, the policy cannot correctly detect and prevent scanning and flood attacks.

Applying an attack defense policy to the device

About this task

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.

Applying an attack defense policy to a device can improve the efficiency of processing attack packets destined for 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.

Procedure

1.     Enter system view.

system-view

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

About this task

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 are destined for the device.

·     Attack type.

·     Attack defense action.

·     Source and destination IP addresses.

·     VPN instance to which the victim IP address belongs.

Restrictions and guidelines

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

Procedure

1.     Enter system view.

system-view

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

About this task

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

Restrictions and guidelines

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.

Procedure

1.     Enter system view.

system-view

2.     Enable TCP fragment attack prevention.

attack-defense tcp fragment enable

By default, TCP fragment attack prevention is enabled.

Enabling the login delay

About this task

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.

Procedure

1.     Enter system view.

system-view

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.

Verifying and maintaining attack detection and prevention

Verifying attack defense configuration

To display attack defense policy configuration, execute the following command in any view:

display attack-defense policy [ policy-name ]

Displaying attack detection and prevention entries

Displaying information about IPv4 addresses protected by flood attack detection and prevention

To display information about IPv4 addresses protected by flood attack detection and prevention, execute the following command in any view:

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 ]

Displaying information about IPv6 addresses protected by flood attack detection and prevention

To display information about IPv6 addresses protected by flood attack detection and prevention, execute the following command in any view:

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 ]

Displaying information about IPv4 scanning attackers

To display information about IPv4 scanning attackers, execute the following command in any view:

display attack-defense scan attacker ip [ [ interface interface-type interface-number | local ] [ slot slot-number ] ] [ count ]

Displaying information about IPv6 scanning attackers

To display information about IPv6 scanning attackers, execute the following command in any view:

display attack-defense scan attacker ipv6 [ [ interface interface-type interface-number | local ] [ slot slot-number ] ] [ count ]

Displaying and clearing attack detection and prevention statistics

Displaying flood attack detection and prevention statistics for an IPv4 address

To display flood attack detection and prevention statistics for an IPv4 address, execute the following command in any view:

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 | local ] [ slot slot-number ] ] [ count ]

Displaying flood attack detection and prevention statistics for an IPv6 address

To display flood attack detection and prevention statistics for an IPv6 address, execute the following command in any view:

display attack-defense { ack-flood | dns-flood | fin-flood | flood | http-flood | icmpv6-flood | rst-flood | syn-flood | syn-ack-flood | udp-flood } statistics ipv6 [ ipv6-address [ vpn vpn-instance-name ] ] [ [ interface interface-type interface-number | local ] [ slot slot-number ] ] [ count ]

Clearing flood attack detection and prevention statistics

To clear flood attack detection and prevention statistics, execute the following command in user view:

reset attack-defense policy policy-name flood protected { ip | ipv6 } statistics

Displaying and clearing attack detection and prevention statistics on an interface

To display attack detection and prevention statistics on an interface, execute the following command in any view:

display attack-defense statistics interface interface-type interface-number [ slot slot-number ]

To clear attack detection and prevention statistics for an interface, execute the following command in user view:

reset attack-defense statistics interface interface-type interface-number

Displaying and clearing attack detection and prevention statistics for the device

To display attack detection and prevention statistics for the device, execute the following command in any view:

display attack-defense statistics local [ slot slot-number ]

To clear attack detection and prevention statistics for the device, execute the following command in user view:

reset attack-defense statistics local

Attack detection and prevention configuration examples

Example: Configuring interface-based attack detection and prevention

Network configuration

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

Configure an attack defense policy and apply the policy to Ten-GigabitEthernet 0/0/7 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 drop the packets sent by the attacker.

·     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

‌

Procedure

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

# Create attack defense policy a1.

<Router> system-view

[Router] attack-defense policy a1

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

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

# Configure low-level scanning attack detection, specify logging and drop as the prevention actions.

[Router-attack-defense-policy-a1] scan detect level low action logging drop

# 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.

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

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

# Apply attack defense policy a1 to Ten-GigabitEthernet 0/0/7.

[Router] interface ten-gigabitethernet 0/0/7

[Router-Ten-GigabitEthernet0/0/7] attack-defense apply policy a1

[Router-Ten-GigabitEthernet0/0/7] quit

Verifying the configuration

# Verify that attack defense policy a1 is successfully configured.

[Router] display attack-defense policy a1

          Attack-defense Policy Information

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

Policy name                        : a1

Applied list                       : XGE0/0/7

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

Exempt IPv4 ACL                    : Not configured

Exempt IPv6 ACL                    : Not configured

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

  Actions: CV-Client verify  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,D

 

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 Ten-GigabitEthernet 0/0/7.

[Router] display attack-defense statistics interface ten-gigabitethernet 0/0/7

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

 SYN flood                           1           5000

Signature attack defense statistics:

 AttackType                          AttackTimes Dropped

 Smurf                               1           0