An MSNBC blog has published the recent findings of a study from Columbia University saying millions of HP printers are vulnerable to a "devastating hack attack".

In essence, the vulnerability is that the LaserJet (InkJet not vulnerable) printers made before 2009 (according to HP) do not check digital signatures before installing a firmware update.  Thus, a specially crafted version of firmware could be remotely installed by creating a crafted printjob including the new firmware version.  The researchers demonstrated overheating a fuser to simulate what kind of physical destruction could incur (it charred the paper but was shut off by a safety before a fire started).  Long story short, for an embedded system (or any system for that matter) if you can rewrite the Operating System you can control the device and make it do all sorts of unintended things.

This isn't the first time HP LaserJet printers have had vulnerabilities, though this is the first time (that I recall at least) of using the firmware to do it.  I think the severity of this vector is somewhat less than portrayed but worth noting, particularly for organizations that operate highly secure environments.

Best practices are likely sufficient to prevent against this attack, namely, you should never have printers (or any other embedded device for that matter) exposed to the Internet.  In theory, you could create malware that infects a PC to then infect a printer but I would suspect such effort would only be used in rare circumstances.  Additionally beyond firewalling the device, network traffic to and from the device could be monitored for traffic other than printjobs which should give indication of a problem.  For instance, any printer initiating an outbound TCP/IP connection is a sign that something is awry.

The study is a helpful reminded that even devices we don't think of as computers can be hacked and do things we don't intend and compromise our security.

Do you monitor printers or other embedded devices in your environment for compromise or otherwise protect them?  Take the poll and feel free to comment below.

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John Bambenek
bambenek \at\ gmail /dot/ com
Bambenek Consulting