This module is used to look for dynamic dns domains that are present in various kinds of network traffic. For HTTP, the HOST header value is checked, for DNS the query request value is checked, and for SSL the server value is checked. Since dynamic DNS domains often take the format of .domain.tld the value in the host header is stripped of everything to the left of domain.tld, in the event that doesn't match the check is expanded to something.domain.tld.

A good place to get started is malware-domains dyndns list, the following will put it in the right format for this script:

wget "http://www.malware-domains.com/files/dynamic_dns.zip" && unzip -c dynamic_dns.zip | tail -n +4 | grep -v ^# | grep -v ^$ | cut -f 1 > tmp.txt && echo -e "#fields\tdomain" > dynamic_dns.txt && cat tmp.txt >> dynamic_dns.txt && rm tmp.txt dynamic_dns.zip

In additon to looking for the presence of dynamic DNS domains it will keep track (for 1 day) all IPs that resolve to a dynamic DNS domain, and flag any traffic destined to those IP addresses

Requires Bro 2.1 Mike ([email protected])