ASA - Botnet Configuration

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This configuration example is meant to be interpreted with the aid of the official documentation from the configuration guide located here:


Malware is malicious software that is installed on an unknowing host. Malware that attempts network activity such as sending private data (passwords, credit card numbers, key strokes, or proprietary data) can be detected by the Botnet Traffic Filter when the malware starts a connection to a known bad IP address. The Botnet Traffic Filter checks incoming and outgoing connections against a dynamic database of known bad domain names and IP addresses (the blacklist), and then logs or blocks any suspicious activity.


Enable DNS client on ASA

This steps is required to allow it to resolve the address of CSIO's updater service, so the dynamic filter update client to fetch updates.

ASA(config)# dns domain-lookup outside ASA(config)#dns server-group DefaultDNS ASA(config-dns-server-group)#name-server

Enable dynamic traffic filtering (Botnet Traffic Filter)

ASA(config)#dynamic-filter updater-client enable

Enable the Botnet Traffic Filter database update

ASA(config)#dynamic-filter use-database

Classify the traffic that will be exempted and subjected.

ASA(config)#access-list botnet-exclude extended deny ip any ---> exempted traffic ASA(config)#access-list botnet-exclude extended permit ip any any ---> subjected traffic

Enable dynamic-filter classification on outside interface

ASA(config)#dynamic-filter enable interface outside classify-list botnet-exclude

Configure a class map and only match dns traffic

ASA(config)#class-map botnet-DNS ASA(config-cmap)# match port udp eq domain

Enable DNS snooping on the external interface

ASA(config)# policy-map botnet-policy ASA(config-pmap)# class botnet-DNS ASA(config-pmap-c)# inspect dns dynamic-filter-snoop

ASA(config)# service-policy botnet-policy interface outside

Alternatively, you can also choose to apply this to the existing global policy that is already configured on the ASA.

class-map inspection_default match default-inspection-traffic ! policy-map global_policy class inspection_default

 inspect dns dynamic-filter-snoop

service-policy global_policy global

Define local whitelists and/or blacklists if needed.

Never block addresses:

This is traffic to or from an IP address that is considered to be good. It is part of administrator configured lists.

ASA(config)# dynamic-filter whitelist ASA(config-llist)# name ASA(config-llist)# name Manual Black List:

This is traffic to or from an IP address that is considered to be malicious. This IP address can be either an IP address/network entry in the dynamic blacklist or administrator configured blacklist, or it can be a snooped IP address that was found in a DNS reply for a blacklisted domain. Whitelist

ASA(config)# dynamic-filter blacklist ASA(config-llist)# name ASA(config-llist)# name ASA(config-llist)# address

Related show Commands

show dynamic-filter data

show dynamic-filter database find <string>

show dynamic-filter reports top botnet-sites

show dynamic-filter reports top infected-hosts

show dynamic-filter reports top botnet-ports

Show running-config

dns domain-lookup outside dns server-group DefaultDNS name-server ! dynamic-filter updater-client enable dynamic-filter use-database


access-list botnet-exclude extended deny ip any access-list botnet-exclude extended permit ip any any ! dynamic-filter enable interface outside classify-list botnet-exclude


class-map botnet-DNS match port udp eq domain ! policy-map botnet-policy class botnet-DNS

 inspect dns dynamic-filter-snoop

! service-policy botnet-policy interface outside

Related Information


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