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Preventing USB Drives From Biting Back

This week, the Florida Free Culture student club hosted a three-day event in which they helped secure student-owned computers at the University of Florida campus by cleaning up malware infections and installing the university site-licensed antivirus software. The event was designed not only to help secure student computers, but to also promote free and open source software by providing educational handouts and installing a variety of applications, including Firefox, Thunderbird, the Gimp, OpenOf
This week, the Florida Free Culture student club hosted a three-day event in which they helped secure student-owned computers at the University of Florida campus by cleaning up malware infections and installing the university site-licensed antivirus software. The event was designed not only to help secure student computers, but to also promote free and open source software by providing educational handouts and installing a variety of applications, including Firefox, Thunderbird, the Gimp, OpenOffice, Pidgin, and more.

Staffed completely by students -- myself being the exception -- we saw a lot of laptops over the three days in various states of needing software updates, including antivirus suites. If I were to guess how many machines had problematic antivirus installations, it would be close to 90 percent, with expired demo versions included with the initial laptop purchase, malware disabling the antivirus, and corrupted, partially uninstalled copies of antivirus due to an attempt to install another antivirus product.One of the club's members put together a custom updated version of the Open CD with the latest versions of the aforementioned software and a copy of the university's site-licensed antivirus software. When I was handed a malware-infested machine, rather than running analysis tools I keep on my incident response flash drive, I decided to download them each time from a trusted Web site. Why go through the trouble? USB flash drives are a very effective means of spreading malware.

We all remember the credit union pentest by Steve Stasiukonis, right? I was recently reminded of the danger of USB flash drives by hogfly's Forensic Incident Response blog entry "Beware the key." I think hogfly says it best with the following:


USB keys are prevalent. They are used heavily by many incident response teams and first responders. They're less fragile than CDs, faster and offer greater storage. They are also weapons of destruction and can become fast victims of compromised systems. It's been estimated that 10% of malware has the ability to infect removable media devices.

Had I used my personal incident response USB flash drive for diagnosing infected machines during the event, it's probable I would have spread it to more machines since a majority of them were lacking proper protection and nearly half had active infections. It wouldn't be the first time I've seen this happen. I know a sysadmin who, when responding to a possible incident two months ago, ended up infecting his own desktop when looking at a student's USB flash drive. While sysadmins promote rebuilding infected hosts, they don't like having to rebuild their own workstation!

Of course, it doesn't help when vendors ship infected devices to you. There have been numerous cases over the last year documented at the SANS Internet Storm Center about infected USB devices, including flash drives shipped by HP and digital photo frames that show up as a removable drive in Windows just like USB flash drives.

We as forensic investigators already know it's a best practice to wipe drives before using them for forensic imaging, but hogfly reminds us that wiping our flash drives between incidents, even between endpoints, is a good practice to add to our incident response methodology.

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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