Re: Request for discussion on defending against specific Nmap TCP syn and version scans.

[revnic () gmail com]

you could run a script that will grep access_log for exploit attempts and add those IPs in iptable's drop list.... also 
there is a patch for iptables that will slow down portscanning.
another thing you could do is change service's banner. 

------------------------------------------------------------------------------
This List Sponsored by: Lancope

"Discover the Security Benefits of Cisco NetFlow"
Learn how Cisco NetFlow enables cost-effective security across distributed 
enterprise networks. StealthWatch, the veteran Network Behavior Analysis (NBA) 
and Response solution, leverages Cisco NetFlow to provide scalable, 
internal network security. 
Download FREE Whitepaper "Role of Network Behavior Analysis (NBA) and Response 
Systems in the Enterprise."

http://www.lancope.com/resource/
------------------------------------------------------------------------------