Land Attack is happening if an attacker sends a forged stream of TCP SYN packets with the same source and destination IP address and TCP port numbers. The SYN flag has to be set. As a result, the system will attempt to reply to itself and t he victim system will be confused and crashed or rebooted. Recent study found the Windows XP with SP 2 and Windows 2003 systems are vulnerable to this attack. Actually Sun OS, BSD and Macs are all found vulnerable to this attack and all these systems share a BSD based TCP/IP stack.

Service providers can block LAND attacks that originate behind aggregation points by installing filters on the ingress ports of their edge routers to check the source IP addresses of all incoming packets. If the address is within the range of advertised prefixes, the packet is forwarded; otherwise it is dropped.

Related Terms: Firewall, Denial of Service, DDOS, TCP