DNS sinkholing helps you to identify infected hosts
on the protected network using DNS traffic in situations where the
firewall cannot see the infected client's DNS query (that is, the
firewall cannot see the originator of the DNS query). In a typical
deployment where the firewall is north of the local DNS server,
the threat log will identify the local DNS resolver as the source
of the traffic rather than the actual infected host. Sinkholing
malware DNS queries solves this visibility problem by forging responses
to the client host queries directed at malicious domains, so that
clients attempting to connect to malicious domains (for command-and-control,
for example) will instead attempt to connect to a default Palo Alto
Networks sinkhole IP address, or to a user-defined IP address as
illustrated in Configure DNS Sinkholing for a List of Custom Domains. Infected hosts
can then be easily identified in the traffic logs because any host
that attempts to connect to the sinkhole IP address is most likely
infected with malware.
If you want to enable DNS sinkholing for Palo Alto Networks DNS
signatures, attach the default Anti-Spyware profile to a security
policy rule (see Set Up Antivirus, Anti-Spyware, and Vulnerability Protection). DNS queries
to any domain included in the Palo Alto Networks DNS signatures
will be resolved to the default Palo Alto Networks sinkhole IP address.
The IP addresses currently are IPv4—126.96.36.199 and a loopback
address IPv6 address—::1. These address are subject to change and
can be updated with content updates.