Editing Port scanner (section)

===ACK scanning===
ACK scanning is one of the more unusual scan types, as it does not exactly determine whether the port is open or closed, but whether the port is filtered or unfiltered. This is especially good when attempting to probe for the existence of a firewall and its rulesets. Simple packet filtering will allow established connections (packets with the ACK bit set), whereas a more sophisticated stateful firewall might not.<ref name=nmapguide>{{cite web | title=Port Scanning Techniques | work=Nmap reference guide | url=http://nmap.org/man/man-port-scanning-techniques.html | year=2001 | access-date=2009-05-07}}</ref>