Thursday, August 18, 2005

Threat Levels: Low, Medium or High? Red, Orange or Yellow?

Microsoft and the AntiVirus Vendors (perhaps a decent name for a band) tend to think of "threat" in terms of the number of machines infected, how many are vulnerable, and certain other primitive measures of damage done by a worm, such as "does it delete data files". By those measures, this worm appears benign. In fact this current crop of worms is far more harmful than some of the most famous worms from a couple years ago. Rather than hitting many millions of machines, these worms hit only a few hundred thousand or a few million perhaps (infestations inside large corporate and government networks are hard to count from the outside, hiding many infected systems.) When the worms are released, they do the most damage in the first few hours. They immediately search the hard drives for interesting files and upload them to remote servers. This damage is done, to the tune of thousands of files and hundreds of MB of data, before you learn which port to block at your firewall. They steal user identity information, documents, and files that store encrypted passwords so they can be cracked at the convenience of the attacker. They often leave very little in the way of evidence about what they have done. If you get lucky and capture an IRC session used to control these things, you'll understand the true nature of the threat. Many infected systems this week were being actively controlled from outside the corporate firewall by hostile forces. I've recently seen a captured IRC session which includes automated traffic from the zombied bots, as well as conversation traffic between members of a team of human attackers who immediately noticed (and thought it was funny) when the client blocked the IRC port published by the antivirus vendors. We have very little forensic evidence on this, but what we do have indicates that the bots appear to have automatically switched to another port/server combination and nary a beat was skipped. Managers at all levels of corporations and government need to understand that these worms are a very serious threat today. Even though the number of systems infected might be smaller than in previous outbreaks, these worms and bots are dramatically more sophisticated. The security industry needs to come up with better measures of the threat level, which include the risk of data theft, identity theft, and execution of arbitrary command and code on internal systems.

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