Internet News published this article yesterday, about zombie PCs (http://www.internetnews.com/security/article.php/3796526/The+Webs+Latest+Threat+Smarter+Zombies.htm) getting smarter and harder to track, as they are regularly asking for new IP addresses from their ISPs, ultimately rendering anti-spam software that works by blocking IPs now useless:

Unfortunately, my first thought reading through this is a big “I told you so” to the universe of security experts who keep insisting that IP reputation is the silver bullet in the ongoing war against spam and other e-mail bourn threats. Commtouch (www.commtouch.com) is a world recognized expert in the field of IP based reputation and should be taken at their word. If they say that IP reputation is finally dead, I would agree.

The fact that IP based reputation schemes are flawed has been well known to Sendio (www.sendio.com) for years. We have always believed the only type of security that really works is active security. All of the current IP reputation schemes are passive/reactive; employing complex algorithms to make guesses based on patterns and probabilities. Clearly, in a world where there is big money at stake, the bad guys are highly motivated to find mechanism that allow them to evade these passive security paradigms.

I believe the time has come for the security community-at-large to recognize that we need to move away from passive guessing schemes to active authentication methodologies.