And you get a POS malware name...and you get a POS malware name....and you get a POS malware name....

This morning I woke up to find Trend Micro/Trend Labs had a new post on an "old undetected PoS malware" which they have called "PwnPOS". I was interested at first, but this looks like just another case of randomly assigning names to malware and/or threat actors. Unfortunately for the folks at Trend, who usually put out pretty good work, the scraper in question (which is an executable file that I have personally seen with many names, but we will refer to it as "wnhelp.exe") is old. Very, very old. In fact, the date/time stamp embedded into the file itself is from 2010.

wnhelp as seen in PEStudio 8.46

The scraper is very basic, it looks through memory looking for Track data, and when it finds matching data, it saves it to a file "perfb419.dat" which is under the Windows/System32 folder. There are sometimes legitimate files with similar names under this path, no doubt it was an effort for the attackers to try to make the data blend in. 

Example of "track" data collected in perfb419.dat. 

The scraper itself does not have an active exfiltration mechanism, so either an additional file(s) is needed to exfil the collected data or the attacker(s) can remotely access the system and send the file out (email, ftp, file sharing site, etc). wnhelp uses a "service" persistence mechanism in order to stay running on the machine, so looking at just CurrentVersion/Run in the Registry will not allow you to detect the file. The service is named "Windows Media Help", and the information that is collected from the Live Response Collection using SysInternals autorunsc is listed below:

wnhelp embedded under the "Windows Media Help" service

The exfiltration methods listed in the Trend article "might" be new, but I cannot be certain as I personally do not have access to those files (yet, I am working on that). I am leery of how new these files may be though, simply based on the liberties that Trend appears to have taken with the original wnhelp file. Additionally, of all the files listed in the Trend post, the most recent compile time is listed as 2012, with most of the compile times dating back to 2010. None of these files appear to be "new" at all. 


Not "new" or "under the radar"


Back in 2013, the wnhelp sample was uploaded to malwr, among other sites, to use their automated malware analysis tool. 

malwr results from 2013

Additionally, a Google search for the md5 hash (c86327222d873fb4e12900a5cadcb849) shows that, at the very least, a user of the domain "systemexplorer.net" posed a question about wnhelp back in 2012. I did not dig through all of the results, but 83 search results, with several entries on the first page relating to "malware" in one form or another, is hardly flying "under the radar".

systemexplorer.net query of wnhelp from 2012

UPDATE (March 6, 2015): As @maldr0id pointed out, the wnhelp file was submitted to virustotal back on October 2, 2012, with a 3/42 detection ratio. Interestingly enough, Trend Micro was one of the three that detected the file as malicious.  The same file was uploaded to virustotal on February 16, 2011. At that time it had a 0/43 detection ratio. 

virustotal results of scraper file, performed on October 2, 2012

virustotal results of scraper file, performed on February 16, 2011

In the Trend post, the author stated "PwnPOS is one of those perfect examples of malware that’s able to fly under the radar all these years". As you can see from just the examples that are listed above, that statement is simply not true. It does highlight the importance of understanding "what" is running within your POS environment. It also highlights the fact of regularly checking systems within your POS environment to make sure that they are running properly and there is nothing "else" (malicious or otherwise) running on those systems.


Several month ago I came across a domain that was hosting this (and other) samples of POS malware. I collected all of the samples and files on the domain. The owners of the domain let the registration lapse a few months ago, at which time I purchased it and re-directed it to "fbi.gov" (my own way of "getting back" at bad actors). If you are interested please feel free to contact me, I will share some of the files with you (I cannot share them all, as some of the files contained information that I legally cannot share).