Microsoft IIS 5.0 is vulnerable to a denial of service attack.
A flaw in the WebDav extensions allow a remote attacker to carry out a DoS by repeatedly requesting nonexistent files via the HTTP LOCK method.
This leads to a complete consumption of memory resources, eventually crashing the host and requiring a restart.
LOCK /aaaaaaaaaaaaaaaaaaaaaaaaaa.htw HTTP/1.0
One way is to combine the attack with asp executions, eg.
GET /iisstart.asp?uc=a HTTP/1.0