DNS spoofing

As mentioned before, DNS, or Domain Name Services, maps a name to an IP address. This process is very similar to the process described earlier with reference to DHCP. When the client supplies a DNS name when making a request for a resource, such as in the URL bar in a browser or when Telnetting or SSHing to a host via the command line, the operating system will first look to its local hosts file to see if a mapping is available there. In most cases, this fails to return a result and the operating system next asks the DNS server to provide the mapping. Where this is similar to DHCP is that when a DNS request is initiated, the client will listen for the first response it hears, with the appropriate sequence number used to test the validity of responses, and then will disregard any DNS replies that come after the initial one. This creates a race condition to return a response back to the client that the attacker wants instead of the legitimate response from the local DNS server...