14-Security Configuration Guide

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10-Attack detection and prevention configuration
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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.

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 top attack statistics ranking feature

5.     (Optional.) Configuring the login attack prevention feature

Typically, this feature is separately used.

¡     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.

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.

Restrictions and guidelines

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 receiving rate of packets destined for an IP address keeps reaching or exceeding the threshold, the device enters prevention state and takes the specified actions. When the rate drops below the silence threshold (three-fourths of the threshold), the device returns to the attack detection state.

An appropriate threshold can effectively prevent attacks. If the global threshold for triggering flood attack prevention is too low, false positives might occur, causing performance degradation or packet loss. If the global threshold is too high, false negatives might occur, making the network defenseless. Therefore, it is a good practice to enable the threshold learning feature for the device to automatically learn the global threshold. This feature allows the device to learn the global threshold based on the traffic flows in the network as follows:

1.     Monitors the packet receiving rate in the network.

2.     Calculates the global threshold based on the peak rate learned within the threshold learning duration.

You can choose to manually apply the learned threshold or configure the device to automatically apply the learned threshold.

The threshold learning feature includes the following modes:

·     One-time learning—The device performs threshold learning only once.

·     Periodic learning—The device performs threshold learning at intervals. The most recent learned threshold always takes effect.

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 } [ 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 } [ 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 } [ 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 } [ 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 } [ 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 [ 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 [ 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 } [ 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 } [ 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 } [ port port-list ] [ threshold threshold-value ] [ action { { drop | logging } * | none } ]

By default, IP address-specific HTTP flood attack detection is not configured.

Configuring threshold learning for flood attack prevention

1.     Enter system view.

system-view

2.     Enter attack defense policy view.

attack-defense policy policy-name

3.     Enable the threshold learning feature for flood attack prevention.

threshold-learn enable

By default, the threshold learning feature for flood attack prevention is disabled.

4.     (Optional.) Set the threshold learning mode.

¡     To set the one-time learning mode:
threshold-learn mode once

¡     To set the periodic learning mode:
threshold-learn mode periodic

By default, the one-time learning mode is used.

5.     (Optional.) Set the threshold learning duration.

threshold-learn duration duration

By default, the threshold learning duration is 1440 minutes.

6.     (Optional.) Set the threshold learning interval.

threshold-learn interval interval

By default, the threshold learning interval is 1440 minutes.

Skip this step for the one-time learning mode.

7.     (Optional.) Set the threshold learning tolerance value.

threshold-learn tolerance-value tolerance-value

By default, the threshold learning tolerance is 50, in percentage.

Skip this step if auto application of the learned threshold is disabled.

8.     (Optional.) Enable auto application of the learned threshold.

threshold-learn auto-apply enable

By default, auto application of the learned threshold is disabled.

9.     Apply the most recent threshold that the device has learned.

threshold-learn apply

This command does not take effect when auto application of the learned threshold is enabled.

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.

·     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.

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.

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 top attack statistics ranking feature

About this task

This feature collects statistics about dropped attack packets based on attacker, victim, and attack type and ranks the top attack statistics by attacker and victim. To display the top attack statistics rankings, use the display attack-defense top-attack-statistics command.

Procedure

1.     Enter system view.

system-view

2.     Enable the top attack statistics ranking feature.

attack-defense top-attack-statistics enable

By default, the top attack statistics ranking feature is disabled.

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.

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

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.

Display and maintenance commands for 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

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 ] [ interface interface-type interface-number | local ] [ count ]

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 ] [ interface interface-type interface-number | local ] [ count ]

Display attack defense policy configuration.

display attack-defense policy [ policy-name ]

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 ] [ count ]

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 ] [ count ]

Display information about IPv4 scanning attackers.

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

Display information about IPv6 scanning attackers.

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

Display attack detection and prevention statistics on an interface.

display attack-defense statistics interface interface-type interface-number

Display attack detection and prevention statistics for the device.

display attack-defense statistics local

Display top 10 attack statistics.

display attack-defense top-attack-statistics { last-1-hour | last-24-hours | last-30-days } [ by-attacker | by-type | by-victim ]

Clear flood attack detection and prevention statistics.

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

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 top 10 attack statistics.

reset attack-defense top-attack-statistics