Nearly every PC has an anti-theft product called Computrace embedded in its BIOS PCI Optional ROM or its unified extensible firmware interface (UEFI). Computrace is a legitimate, trusted application developed by Absolute Software. However, it often runs without user-consent, persistently activates itself at system boot, and can be exploited to perform various attacks and to take complete control of an affected machine. Kaspersky Lab researchers Vitaly Kamluk and Sergey Belov along with Anibal Sacco of Cubica Labs
earlier presented their research in a briefing titled "Absolute Computrace Revisited" six months ago at the Kaspersky Security Analyst Summit (SAS) in the Dominican Republic. They presented an updated version of that talk at Black Hat last week.
Computrace should not be enabled by default. Absolute Software's technical documentation says that Computrace should be enabled either by the user or by IT departments with admin control of work machines. In fact, to this point, Kamluk, Sacco and Belov can only guess at how Computrace is enabled by default on many out-of-the-box PCs. At present they believe the software is being unintentionally initiated by manufacturers. Furthermore, once Computrace is enabled, it is incredibly persistent and very difficult to remove or even turn off. One of the problems – as was highlighted at SAS – is that Computrace does not enforce encryption when it communicates and it does not verify the identity of the remote server from which it receives commands. This is particularly irksome given how Computrace works: first the persistence modules in BIOS/UEFI update a system's default autochk.exe. Then the new autochk.exe drops and registers a new system service called rpcnetp. Rpcnetp, in turn, talks to the Absolute server and is replaced by rcpnet, which is a core remote administration module that is restored if the user deletes it. In other words, the way Computrace interacts with Absolute could expose users to man-in-the-middle attacks. Back in February, Kamluk described Computrace's exploitability as follows:
The software is extremely flexible. It's a tiny piece of code which is a part of the BIOS. As far as it is a piece of the BIOS, it is not very easy to update the software as often. So they made it very extensible. It can do nearly anything. It can run every type of code. You can do to the system whatever you want. Considering that the software is running on these local system privileges, you have full access to the machine. You can wipe the machine, you can monitor it, you can look through the webcam, you can actually copy any files, you can start new processes. You can do absolutely anything.