After sinkhole action is defined for a DNS
signature source, specify an IPv4 and/or IPv6 address that will
be used for sinkholing. By default, the sinkhole IP address is set
to a Palo Alto Networks server. You can then use the traffic logs
or build a custom report that filters on the sinkhole IP address
and identify infected clients. The following is the sequence
of events that will occur when an DNS request is sinkholed: Malicious
software on an infected client computer sends a DNS query to resolve
a malicious host on the Internet. The client's DNS query is
sent to an internal DNS server, which then queries a public DNS
server on the other side of the firewall. The DNS query matches
a DNS entry in the specified DNS signature database source, so the
sinkhole action will be performed on the query. The infected
client then attempts to start a session with the host, but uses
the forged IP address instead. The forged IP address is the address
defined in the Anti-Spyware profile DNS Signatures tab when the
sinkhole action is selected. The administrator is alerted
of a malicious DNS query in the threat log, and can then search
the traffic logs for the sinkhole IP address and can easily locate
the client IP address that is trying to start a session with the
sinkhole IP address. |