ASA - Botnet Configuration
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Introduction
This configuration example is meant to be interpreted with the aid of the official documentation from the configuration guide located here:
http://www.cisco.com/en/US/docs/security/asa/asa82/configuration/guide/conns_botnet.htm
Overview
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.
Configuration
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 64.102.6.247
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 192.168.0.0 255.255.0.0 ---> 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 www.google.com ASA(config-llist)# name www.cisco.com 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 www.crackhell.com ASA(config-llist)# name www.megaport.hu ASA(config-llist)# address 164.109.48.46 255.255.255.255
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 64.102.6.247 ! dynamic-filter updater-client enable dynamic-filter use-database
!
access-list botnet-exclude extended deny ip any 192.168.0.0 255.255.0.0 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
Logging
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http://www.cisco.com/en/US/docs/security/asa/asa82/system/message/logmsgs.html#wp5787165
