p0f: p0f (passive os fingerprint tool)
p0f:
p0f: p0f is a passive operating system fingerprinting tool.  It can
p0f: identify the OS on machines that connect to your box, machines you
p0f: connect to, machines you cannot connect to, and machines whose
p0f: communications you can observe.  It can detect or measure firewall
p0f: presence, NAT use, existence of a load balancer setup, the distance
p0f: to the remote system, its uptime, and its network hookup and ISP.
p0f:
p0f: Homepage: http://lcamtuf.coredump.cx/p0f3/
p0f: