Chapter 26 Configuring the Botnet Traffic Filter

Configuring the Botnet Traffic Filter

For example, you receive the following syslog message:

ASA-4-338002: Dynamic Filter permitted black listed TCP traffic from inside:10.1.1.45/6798 (209.165.201.1/7890) to outside:209.165.202.129/80 (209.165.202.129/80), destination 209.165.202.129 resolved from dynamic list: bad.example.com

You can then perform one of the following actions:

•Create an access rule to deny traffic.

For example, using the syslog message above, you might want to deny traffic from the infected host at 10.1.1.45 to the malware site at 209.165.202.129. Or, if there are many connections to different blacklisted addresses, you can create an ACL to deny all traffic from 10.1.1.45 until you resolve the infection on the host computer.

For the following syslog messages, a reverse access rule can be automatically created from the Real Time Log Viewer:

–338001, 338002, 338003, 338004 (blacklist)

–338201, 338202 (greylist)

See Chapter 41, “Configuring Logging,” in the general operations configuration guide and

Chapter 7, “Configuring Access Rules,” for more information about creating an access rule.

Note If you create a reverse access rule form a Botnet Traffic Filter syslog message, and you do not have any other access rules applied to the interface, then you might inadvertently block all traffic. Normally, without an access rule, all traffic from a high security to a low security interface is allowed. But when you apply an access rule, all traffic is denied except traffic that you explicitly permit. Because the reverse access rule is a deny rule, be sure to edit the resulting access policy for the interface to permit other traffic.

ACLs block all future connections. To block the current connection, if it is still active, enter the clear conn command. For example, to clear only the connection listed in the syslog message, enter the clear conn address 10.1.1.45 address 209.165.202.129 command. See the command reference for more information.

•Shun the infected host.

Shunning blocks all connections from the host, so you should use an ACL if you want to block connections to certain destination addresses and ports. To shun a host, enter the following command in Tools > Command Line Interface. To drop the current connection as well as blocking all future connections, enter the destination address, source port, destination port, and optional protocol.

shun src_ip [dst_ip src_port dest_port [protocol]]

For example, to block future connections from 10.1.1.45, and also drop the current connection to the malware site in the syslog message, enter:

shun 10.1.1.45 209.165.202.129 6798 80

After you resolve the infection, be sure to remove the ACL or the shun. To remove the shun, enter no shun src_ip.

Searching the Dynamic Database

If you want to check if a domain name or IP address is included in the dynamic database, you can search the database for a string.

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ASA Services Module, ASA 5555-X, ASA 5545-X, ASA 5585-X, ASA 5580 specifications

Cisco Systems has long been a leader in the field of network security, and its Adaptive Security Appliance (ASA) series is a testament to this expertise. Within the ASA lineup, models such as the ASA 5505, ASA 5580, ASA 5585-X, ASA 5545-X, and ASA 5555-X stand out for their unique features, capabilities, and technological advancements.

The Cisco ASA 5505 is designed for small businesses or branch offices. It provides essential security features such as firewall protection, flexible VPN capabilities, and intrusion prevention. The ASA 5505 supports a user-friendly interface, allowing for straightforward management. Its built-in threat detection and prevention tools provide a layered defense, and with scalability in mind, it can accommodate various expansion options as organizational needs grow.

Moving up the line, the ASA 5580 delivers greater throughput and advanced security features. This model is suited for medium to large enterprises that require robust protection against increasingly sophisticated threats. Its multi-core architecture allows it to manage high volumes of traffic seamlessly while maintaining excellent performance levels. The ASA 5580 also supports application-layer security and customizable access policies, making it highly adaptable to diverse security environments.

The ASA 5585-X further enhances Cisco's security offerings with advanced malware protection and extensive security intelligence capabilities. It incorporates next-generation firewall features, including context-aware security, and supports advanced threat detection technologies. This model is ideal for large enterprises or data centers that prioritize security while ensuring uninterrupted network performance and availability.

For enterprises requiring a balance of performance and security, the ASA 5545-X presents a compelling option. This model features scalable performance metrics, high availability, and integrated advanced threat protection. Coupled with advanced endpoint protection and detailed monitoring capabilities, the ASA 5545-X enables organizations to manage their security posture effectively.

Lastly, the ASA 5555-X blends cutting-edge technologies with strong security infrastructures. It boasts high throughput and the ability to execute deep packet inspections. Its sophisticated architecture supports threat intelligence feeds that provide real-time security updates, making it a powerful tool against modern threats.

Each of these Cisco ASA models brings specific advantages to varied environments. Their integrative capabilities enable businesses to enhance their security postures while benefiting from seamless scalability and management. As cybersecurity threats evolve, these advanced appliances play a vital role in protecting valuable digital assets.
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