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Manual Chapter: Detecting and preventing SIP DoS Attacks
Manual Chapter
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Detecting and preventing SIP DoS Attacks

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

Session Initiation Protocol (SIP) is a signaling protocol that is typically used to control communication sessions, such as voice and video calls over IP. On the BIG-IP® system, SIP attack detection detects and automatically drops SIP packets that are malformed or contain errors. In addition, you can use a SIP denial-of-service (DoS) profile to log unusual increases in SIP request packets, including packets that are malformed, packets that contain errors, or packets of any other type that appear to rapidly increase.

You can use the SIP DoS Protection profile to configure the percentage increase over the system baseline that indicates a possible attack is in progress on a particular SIP request type, or an increase in anomalous packets. Later, you can use reporting or logging functions to detect such packets. This is a reporting and tracking function only.

Important: To use SIP DoS protection, you must create a SIP profile, and attach it to the virtual server to which the SIP DoS feature is applied.

Task list

Detecting SIP denial-of-service attacks with a DoS profile

In this task, you create the DoS Protection profile and configure SIP settings at the same time. However, you can configure SIP attack detection settings in a DoS profile that already exists.
The BIG-IP® system handles SIP 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 SIP 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. Under Profile Information, click General Settings, and in the Profile Name field, type the name for the profile.
  4. To configure SIP security settings, click Protocol SIP Protection, click Edit in the far right column, then select Enabled.
  5. To enable attack detection based on the rate of protocol errors, next to Protocol Errors Attack Detection, click Edit in the far right column, then 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. In the Rate threshold field, type the rate of packets with errors per second to detect.
    This threshold sets an absolute limit which, when exceeded, registers an attack.
  8. In the Rate limit field, type the absolute limit for packets per second with protocol errors. Packets that exceed this limit are dropped.
  9. To change the threshold or rate increase for a particular SIP method, in the SIP Method Attack Detection settings, click Edit in the far right column, select the Enabled check box for each request type that you want to change, then change the values for Threshold, Rate Increase and Rate Limit in the associated fields.
    For example, to change the threshold for NOTIFY requests to 9,999 per second, or an increase of 250% over the average, select the Enabled check box next to notify, then set the Threshold field to 9999 and the Rate Increase field to 250. To rate limit such requests to 33,000 packets per second, set the Rate Limit field to 33000.
    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: SIP request detection allows you to configure the thresholds at which the firewall registers an attack. However, packets are dropped at the Rate Limit setting, not at the attack detection threshold.
  10. To detect IP address sources from which possible attacks originate, enable Bad Actor Detection.
  11. In the Per Source IP Detection (PPS) field, specify the number of packets of this type per second from one IP address that identifies the IP source as a bad actor, for purposes of attack detection and logging.
  12. In the Per Source IP Rate Limit (PPS) field, specify the number of packets of this type per second from one IP address, above which rate limiting or leak limiting occurs.
  13. To automatically blacklist bad actor IP addresses, select Blacklist Attacking Address.
    Note: Automatic IP address blacklisting is enabled only when Bad Actor Detection is enabled.
  14. In the Blacklist Detection Period field, specify the duration in seconds after which the attacking endpoint is blacklisted. By default, the configuration adds an IP address to the blacklist after one minute (60 seconds). Enabled.
  15. In the Blacklist Duration field, specify the amount of time in seconds that the address will remain on the blacklist. The default is 14400 (4 hours).
  16. From the Blacklist Category list, select a black list category to apply to automatically blacklisted addresses.
  17. To allow IP source blacklist entries to be advertised to edge routers so they will null route their traffic, select Allow Advertisements.
    Note: To advertise to edge routers, you must configure a Blacklist Publisher at Security > Options > Blacklist Publisher for the blacklist category.
  18. Click Update to save your changes.
You have now configured a DoS Protection profile to provide custom responses to malformed SIP attacks, and SIP flood attacks, and to allow such attacks to be identified in system logs and reports.
Associate the DoS Protection profile with a virtual server to apply the settings in the profile to traffic on that virtual server. When a SIP attack on a specific query type is detected, you can be alerted with various system monitors.

Assigning a SIP 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 SIP Profile list, select the name of the SIP profile that you previously created.
  5. Click Update.
The virtual server now uses the SIP settings from the SIP profile.

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. In the Destination Address field, type the IP address in CIDR format.
    The supported format is address/prefix, where the prefix length is in bits. For example, an IPv4 address/prefix is 10.0.0.1 or 10.0.0.0/24, and an IPv6 address/prefix is ffe1::0020/64 or 2001:ed8:77b5:2:10:10:100:42/64. When you use an IPv4 address without specifying a prefix, the BIG-IP® system automatically uses a /32 prefix.
  4. On the menu bar, 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 individual addresses to bypass DoS checks

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. To use an address list as a source whitelist, select the address list from Source Address List.
  3. Click Create.
    The New White List Configuration screen opens.
  4. In the Name field, type a name for the whitelist entry.
  5. In the Description field, type a description for the whitelist entry.
  6. From the Protocol list, select the protocol for the whitelist entry.
    The options are Any, TCP, UDP, ICMP, or IGMP.
  7. In the Source area, specify the IP address and VLAN combination that serves as the source of traffic that the system recognizes as acceptable to pass the DoS checks.
    You can also use Any to specify any address or VLAN.
  8. For the Destination setting, specify the IP address and port combination that serves as the intended destination for traffic that the system recognizes as acceptable to pass DoS checks.
    You can also use Any to specify any address or port.
  9. Click Finished to add the whitelist entry to the configuration. Click Repeat to add the whitelist entry, and start 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 SIP DoS Protection Logging profile

Create a custom Logging profile to log SIP 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 SIP DoS Protection area, from the Publisher list, select the publisher that the BIG-IP system uses to log SIP DoS events.
    You can specify publishers for other DoS types in the same profile, for example, for DNS or Application DoS Protection.
  5. Click Finished.
Assign this custom SIP 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 network firewall security 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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