Forcepoint Finds New Malware Hiding in PoS Machines

Forcepoint researchers have found a new strain of Point of Sale (PoS) malware that hides its activities by mimicking the traffic generated by a legitimate remote login service that is used to manage PCs and other systems.

The PoS strain has no connection to the LogMeIn service, which is only used as a decoy, according to research published by Robert Neumann and Luke Somerville on February 8.

Named UDPoS by the Forcepoint team, the malware appears to be a LogMeIn service pack which generated notable amounts of "unusual" DNS requests. This UDP-based DNS traffic is why the strain has that moniker.

PoS malware is looking for the information present in magnetic stripes on a credit card, usually aggregating them until they are sent to a command-and-control (C&C) server. This information may be used to duplicate the card, or perform other types of financial skullduggery.

(Source: Wikipedia)

Forcepoint found that the malware, which shows up as logmeinumon.exe, would link to a C&C server that was hosted in Switzerland. It contained a dropper program, as well as self-extracting archives that would extract content to temp directories on the victim hardware.

A LogMeInUpdService directory is first created along with a system service that will enable persistence once created.

The nasty work continues with the creation of a system monitor that has almost the identical structure of the LogMeIn service component. This monitor directs the malware activity in the next stages.

The Forcepoint researchers were struck by how well the fake acted like a legitimate component:

"It's compiled by the same Visual Studio build and uses the same string encoding technique: both executables contain only a few identifiable plain-text strings, and instead use a basic encryption and encoding method to hide strings such as the C2 server, filenames, and hard-coded process names."

These techniques make it rather hard to differentiate the two.

The monitor component is a multi-threaded application -- despite its small 88kB size -- creating five different threads after its initialization code is completed. It also carries out anti-AV and anti-VM activity.

During its first run, the malware will run DNS query on the C2 address that is embedded in the code. It also finds out the external IP address of the infected machine using an HTTP GET request.

It will then make a batch file, which will hold the fingerprint of the infected machine. This batch file will have within it the network, system, route and process related information. This data is written to a local file called PCi.jpg and sent to the C2 server via DNS.

The malware will then communicate from this point via one of five DNS messages.

Forcepoint researchers believe that this malware strain remains under development. Writing to disk rather than keeping things in-memory, while leaving traces, and the methods of fingerprinting and data collection do not seem optimized. Yet, these techniques are serviceable and functional.

Consumers may not be able to help in mitigation, since the PoS does not run on their own personal hardware. Keeping aware of their credit card activity may show an outbreak after it happens, but the merchant must also keep an eye on their machines as well.

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— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.