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Linux vulnerable to Windows-style autorun exploits

Caveats abound

A security researcher has demonstrated how it might be possible to perform autorun-style attacks against weakly secured Linux PCs.

Windows worms including Conficker and Stuxnet have often spread onto networks after infected USB sticks were plugged into PCs. This has happened automatically in cases where autorun was enabled, as it did in default on older versions of Windows until a change pushed by Microsoft on Tuesday. With autorun-enabled executable files run with minimal user interaction.

Research by Jon Larimer, of IBM's X-Force security division, shows that the issue of autorun causing possible mischief is not (as might have been previously thought) wholly irrelevant to Linux boxes. Larimer developed a demo to show how it might be possible to insert a USB stick with modified code into a Ubuntu PC to get rid of a screensaver without entering a password – and display the user's desktop.

The demo relied on taking advantage of a flaw in GNOME Evince document viewer that was patched in January and, even so, was kind of "weak" because it was shown on a machine with in-built exploit mitigation disabled, as Larimer himself clearly explains.

During a talk at last weekend's ShmooCon security conference Larimer explains how these mitigations – namely ASLR and AppArmor – might be defeated. This aspect of his research was not included in the demo simply to make sure that the demonstration was reliable and he didn't have to mess around trying to run a brute-force attack on ASLR in front of a live audience.

The upshot of the research is that you might be able to do things you aren't supposed to do on a Linux box by misusing autorun functionality. It doesn't mean that Linux autorun worms might be created using the sort of jiggery-pokery illustrated by Larimer.

Even leaving aside the fact that the minuscule ecosystem of Linux malware strains are dwarfed by orders of magnitude by the Windows virus hoard, plenty of other caveats apply, as Larimer makes clear.

More on Larimer's research can be found in a blog post here and in a YouTube video clip of his presentation. ®

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