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 IP address that you define if you choose to Configure DNS Sinkholing for a List of Custom Domains). Infected hosts can then be easily identified in the traffic logs.