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Manual Chapter : Detecting and Preventing DNS DoS Attacks

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BIG-IP AFM

  • 11.5.10, 11.5.9, 11.5.8, 11.5.7, 11.5.6, 11.5.5, 11.5.4, 11.5.3, 11.5.2, 11.5.1
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Detecting and Preventing DNS DoS Attacks

About configuring the BIG-IP system to detect DNS DoS attacks

DNS DoS protection is a type of protocol security. DNS attack detection and prevention serves two functions:

  • To detect and automatically drop DNS packets that are malformed or contain errors.
  • To log unusual increases in DNS packets of any type, including packets that are malformed, packets that contain errors, or packets of any other type that appear to rapidly increase.

You can use the DNS DoS Protection profile to configure the percentage increase over the system baseline, which indicates that a possible attack is in process on a particular DNS query type, or an increase in anomalous packets. Later, you can use reporting or logging functions to detect such packets, and you can use the DNS Security profile to drop packets with specific query types or header opcodes.

You can define whitelist addresses that the DoS check allows. A whitelist DoS address is passed by the DoS profile, without being subject to the checks in the DoS profile.

DNS DoS protection requires that your virtual server includes a DNS profile, and a DoS profile that includes DNS protocol security.

Task summary

Detecting and protecting against DNS denial-of-service attacks with a DoS profile

You can configure DNS attack settings in a DoS profile that already exists.
The BIG-IP® system handles DNS attacks that use malformed packets, protocol errors, and malicious attack vectors. Protocol error attack detection settings detect malformed and malicious packets, or packets that are employed to flood the system with several different types of responses. You can configure settings to identify DNS attacks with a DoS profile.
  1. On the Main tab, click Security > DoS Protection > DoS Profiles .
    The DoS Profiles list screen opens.
  2. Click Create.
    The Create New DoS Profile screen opens.
  3. In the Profile Name field, type the name for the profile.
  4. To configure DNS security settings, next to Protocol Security (DNS), select Enabled.
  5. To enable attack detection based on the rate of protocol errors, next to Protocol Errors Attack Detection, select Enabled.
  6. In the Rate Increased by % field, type the rate of change in protocol errors to detect as anomalous.
    The rate of detection compares the average rate over the last minute to the average rate over the last hour. For example, the 500% base rate would indicate an attack if the average rate for the previous hour was 100000 packets/second, and over the last minute the rate increased to 500000 packets/second.
  7. To change the threshold or rate increase for a particular DNS query type, in the DNS Query Attack Detection area, select the Enabled check box for each query type that you want to change, then change the values for Threshold and Rate Increase in the associated fields.
    For example, to change the threshold for IPv6 address requests, select the Enabled check box next to aaaa, then set the threshold for packets per second and the rate increase percentage to be considered an attack.
    The Rate Increase compares the average rate over the last minute to the average rate over the last hour. For example, the 500% base rate would indicate an attack if the average rate for the previous hour was 100000 packets/second, and over the last minute the rate increased to 500000 packets/second.
    Note: DNS Query Attack Detection allows you to configure the thresholds at which the firewall registers an attack. However, no packets are dropped if an attack is detected.
  8. Click Update to save your changes.
You have now configured a DoS Protection profile to provide custom responses to malformed DNS attacks, and DNS flood attacks, and to allow such attacks to be identified in system logs and reports.
Associate a DNS profile with a virtual server to enable the virtual server to handle DNS traffic. Associate the DoS Protection profile with a virtual server to apply the settings in the profile to traffic on that virtual server. When a DNS attack on a specific query type is detected, you can configure the DNS security profile to drop packets of a query type that appears to be an attack vector.

Creating a custom DNS profile to firewall DNS traffic

Ensure that you have a DNS security profile created before you configure this system DNS profile.
You can create a custom DNS profile to configure the BIG-IP® system firewall traffic through the system.
  1. On the Main tab, click Local Traffic > Profiles > Services > DNS .
    The DNS profile list screen opens.
  2. Click Create.
    The New DNS Profile screen opens.
  3. In the Name field, type a unique name for the profile.
  4. In the Parent Profile list, accept the default dns profile.
  5. Select the Custom check box.
  6. From the DNS Security list, select Enabled.
  7. From the DNS Security Profile Name list, select the name of the DNS firewall profile.
  8. Click Finished.
Assign the custom DNS profile to the virtual server that handles the DNS traffic that you want to firewall.

Assigning a DNS profile to a virtual server

  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of the virtual server you want to modify.
  3. From the Configuration list, select Advanced.
  4. From the DNS Profile list, select the profile you want to assign to the virtual server.
  5. Click Update.
The virtual server now handles DNS traffic.

Associating a DoS profile with a virtual server

You must first create a DoS profile separately, to configure denial-of-service protection for applications, the DNS protocol, or the SIP protocol.
You add denial-of-service protection to a virtual server to provide enhanced protection from DoS attacks, and track anomalous activity on the BIG-IP® system.
  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of the virtual server you want to modify.
  3. For the Destination setting, select Host and in the Address field, type the IP address for the virtual server.
  4. From the Security menu, choose Policies.
  5. To enable denial-of-service protection, from the DoS Protection Profile list, select Enabled, and then, from the Profile list, select the DoS profile to associate with the virtual server.
  6. Click Update to save the changes.
DoS protection is now enabled, and the DoS Protection profile is associated with the virtual server.

Allowing addresses to bypass DoS checks with a whitelist

You can specify whitelist addresses that the DoS profile and DoS Device Configuration do not subject to DoS checks. Whitelist entries are shared between the Dos Protection profile and the DoS Device Configuration.
  1. On the Main tab, click Security > DoS Protection > White List .
    The DoS Protection White List screen opens.
  2. Click Create.
    The New White List Configuration screen opens.
  3. In the Name field, type a name for the whitelist entry.
  4. In the Description field, type a description for the whitelist entry.
  5. From the Protocol list, select the protocol for the whitelist entry. You can select TCP, UDP, or ICMP.
  6. In the Source area, specify a source address to allow to pass the DoS checks, or select any address. You can also specify a source VLAN to pass DoS checks, or any VLAN.
  7. In the Destination area, specify a destination address to allow to pass the DoS checks, or select any address. You can also specify a destination port to pass DoS checks, or any port.
  8. Click Finished to add the whitelist entry to the configuration. Click Repeat to add the whitelist entry, and star a new entry.
    You can add up to eight DoS whitelist entries to the configuration.
You have now configured whitelist addresses that are allowed to bypass DoS checks.

Creating a custom DoS Protection Logging profile

Create a custom Logging profile to log DoS Protection events and send the log messages to a specific location.
  1. On the Main tab, click Security > Event Logs > Logging Profiles .
    The Logging Profiles list screen opens.
  2. Click Create.
    The New Logging Profile screen opens.
  3. Select the DoS Protection check box.
  4. In the DNS DoS Protection area, from the Publisher list, select the publisher that the BIG-IP system uses to log DNS DoS events.
    You can specify publishers for other DoS types in the same profile, for example, for SIP or Application DoS Protection.
  5. Click Finished.
Assign this custom DoS Protection Logging profile to a virtual server.

Configuring an LTM virtual server for DoS Protection event logging

Ensure that at least one Log Publisher exists on the BIG-IP® system.
Assign a custom DoS Protection Logging profile to a virtual server when you want the BIG-IP system to log DoS Protection events on the traffic the virtual server processes.
Note: This task applies only to LTM®-provisioned systems.
  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of the virtual server you want to modify.
  3. On the menu bar, click Security > Policies .
    The screen displays Policy settings and Inline Rules settings.
  4. From the Log Profile list, select Enabled. Then, for the Profile setting, move the profiles that log specific events to specific locations from the Available list to the Selected list.
  5. Click Update to save the changes.
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