Today I checked my Temp folder, and I found two things I did not expect to see - a "Low" folder and a file titled NitroSysFonts01.dat, both created at exactly the same time yesterday. These I already know are created when I open Internet Explorer and a PDF file respectively (I use Nitro Pro to read PDFs). This concerned me as I had not used either in a while (I exclusively use Firefox), and my thoughts were that something had tried to open a PDF in Explorer. I immediately scanned my laptop with Malwarebytes Antimalware. I ran a custom scan which did not detect anything, but what I noticed was that it took an extremely long time - about 10 minutes or so - to complete the "heuristic analysis" section of the scan, which usually finishes much quicker. This was the same again when running a threat scan later on.
After this I tried to run another scan using Windows Defender, and I ran into some problems.
The first time I started scanning, the scan appeared to freeze for about 20 seconds before starting. Also, the "items scanned" number was extremely high already - in excess of 1,600,000. After about 8 minutes the scan abruptly stopped. I tried to scan again, but was shown an error message saying:
"This service couldn't be started. The group or resource is not in the correct state to perform the requested operation.
Error code: 0x8007139f"
Only by closing and then re-starting Defender could I scan again. This time the scan lasted about 30 minutes before stopping, the same as again. Also notable is that the number by "items scanned" seemed to be the same as it was when the previous scan stopped.
From googling the error code it seems that this message appears if you have two conflicting antivirus programs, but I had since closed MBAM and I run no other program.
I am experiencing no other symptoms or signs of infection, but perhaps worth noting is that I briefly lost my internet connection after the second attempted Defender scan (this may be unrelated). I use Windows 8.1 if this is relevant.
Edited by Osprey95, 22 December 2014 - 11:58 AM.