A fast half-open portscanner. This tool will send TCP packets with the SYN flag set at the destination address. SynScan will send traffic as fast as the host network interface can support.

Based on SynScan version 1.6 by psychoid/tCl (lam3rz.de) with the following changes:
Fixes for several format string overflows and other bugs
Split into multiple programs for sending and receiving of SYN packets
Added a seperate "sslog" tool which only logs open ports and doesn't perform further checks
Support for identifying samba servers in synscand
Support for querying the Server: header on HTTP servers
Support for Open X11 server scanning
Ported to Solaris and IRIX operating systems
Adjusted scan timing to provide for much faster network scanning
Added support for IPv6 (currently in beta)
BindShell.Net: SynScan

It's a very fast and robust syn scanner, compiles without hassles in Backtrack, and it's from the authors of BeEF.