If you see an error in your http logs similar to this.

client sent HTTP/1.1 request without hostname (see RFC2616 section 14.23): /w00tw00t.at.ISC.SANS.DFind:)

Don’t worry too much about it. Someone is just probing your machine.

For more information of the tool that is generating the log entry have a look at Dfind. Dfind is a tool kids use to check for exploits.