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Perimeter

3/30/2009
04:36 PM
John H. Sawyer
John H. Sawyer
Commentary
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Conficker Detection: Let Me Count The Ways

The Internet has been abuzz with information about Conficker. First, it was something along the lines of the sky is falling and will land on April 1st. Then, we were told that April 1st wasn't a big deal because nearly all of the doom and gloom prophecies from the media were about features already in Conficker. Today, we saw a mass release of updates and a couple of new tools for detecting systems alr

The Internet has been abuzz with information about Conficker. First, it was something along the lines of the sky is falling and will land on April 1st. Then, we were told that April 1st wasn't a big deal because nearly all of the doom and gloom prophecies from the media were about features already in Conficker. Today, we saw a mass release of updates and a couple of new tools for detecting systems already compromised by Conficker. How should you go about detecting Conficker in your environment? Oh, let me count the ways...The different ways to check for Conficker-infected hosts through network scanning went from zero to about a dozen today. It seems that all of the major vulnerability scanning vendors have released updates in the past 12- to 24 hours that can detect Conficker infections by scanning TCP port 445 and detecting a change in how the vulnerable section of code responds (the part responsible for MS08-067). Dan Kaminsky worked with some members of the Honeynet Project to develop the detection that was shared through the Conficker Working Group so that "enterprise-class scanners should already be out from Tenable (Nessus), McAfee/Foundstone, nmap, ncircle, and Qualys."

I can't vouch for all of the tools listed in the list Kaminsky included on his blog, but I did spend quite a bit of time testing Nmap, Simple Conficker Scanner (Honeynet Project), and Tenable Nessus this morning, and they pretty much all had the same results. The only real difference is price; the first two tools are free, while Nessus is only free for home users. Corporate users pay a pretty reasonable $1,200 per year.

Of the three tools I've used, Nmap has been the top performer in regard to speed, followed by Nessus and the Simple Conficker Scanner (SCS). The SCS tool is Python-based, which Kaminsky has ported to Windows with py2exe so admins aren't required to install Python to use. The SCS tool wasn't very fast, although I did find that by performing an Nmap of the network first to find hosts listening on port 445/tcp and feeding that list to SCS, the scan time for SCS was greatly reduced. However, at that point, you might as well use Nmap.

Companies already using a commercial vulnerability scanner, like Nessus, should find it easy to enable the detection and make it part of the regular scanning cycle. For example, one of the groups I work with has a 24/7 process for vulnerability scanning to help detect problems before they get out of hand. They use Nessus and Snort to monitor for problems, which are many because of the nomadic nature of the hosts that visit their network. Enabling the check for them was a no-brainer, and now they have another tool, in addition to their IDS, to detect Conficker infections.

If you've not heard from your vulnerability scanning vendor about an update for Conficker, it's time to go knocking on its door and ask why. Considering how many vendors, and free tools, have been updated, if your vendor hasn't provided an update, then you might want to start asking whether they're doing their best to serve you as a customer. Also, having free tools that work consistently well will provide you with the ability to verify what your commercial tool is claiming to do -- something to always keep in mind.

John H. Sawyer is a senior security engineer on the IT Security Team at the University of Florida. The views and opinions expressed in this blog are his own and do not represent the views and opinions of the UF IT Security Team or the University of Florida. When John's not fighting flaming, malware-infested machines or performing autopsies on blitzed boxes, he can usually be found hanging with his family, bouncing a baby on one knee and balancing a laptop on the other. Special to Dark Reading.

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