FakeAV

All posts tagged FakeAV

This fake antivirus software calling itself “Security Tool” intercepts binary files at the point of execution terminates it. Weather it be a bat, com or exe extension the fake av terminates them upon execution. This can be very frustrating when trying to remove this malware on a standalone machine. Fortunately not all processes get terminated; Internet Explorer (iexplore.exe) and Windows Explorer (explorer.exe) do load up so we can use these to our advantage. Our main goal would be to locate and remove this fake av software. Running explorer.exe from start..run will load up the explorer window and from there we can browse to well known locations where the fake av software usually gets dropped.

C:\WINDOWS\
C:\WINDOWS\system32\
C:\Documents and Settings\All Users\Application Data\
C:\Documents and Settings\{username}\Application Data\
C:\Documents and Settings\{username}\Local Settings\Application Data\

Look for unusual files or folders in these locations and if found then rename and reboot. If your pc boots up normally then go the folder which you renamed earlier and delete the malware. In this case this fake av software was called 29225727.exe and was located in

C:\Documents and Settings\{username}\Application Data\

Make sure in your folder options “Show hidden files and folders” is selected before browsing as it might have a hidden attribute set.

Another way you can locate the malware is by searching for the file through Windows Explorer. You can search for files for a certain date, for only exe’s, etc. To get an idea on what the executable file might be called you can browse to the C:\WINDOWS\Prefetch\ folder and see last few files written and search for those executables.

Finally another way is by right-clicking on the shortcut from start..programs..Security Tool menu (if exists) and take note of the path then just go to the path, rename and reboot.

Another fake antivirus software calling itself “XP Guardian 2010″ is doing its rounds displaying bogus pop-ups and fake scans enticing you to buy its product. What is interesting about this malware is that this one changes the machine exe associations in the Windows registry. When any executable with an exe extension is manually or automatically run this malware is loaded first which then calls the original executable.

When an executable is first run it checks various entries in the registry before loading the program. Once a machine has been infected by this malware the call is hijacked to first load the fake antivirus set in the registry

C:\Documents and Settings\{username}\Local Settings\Application Data\av.exe” /START “%1″ %*”

Here the malware av.exe is run followed by the actual executable. The malware has been developed to call the real program after its own program has loaded.

Another interesting entry in the registry made by the malware is when an executable is called Windows checks another location in the registry. This entry is not available in HKEY_CURRENT_USER but even if it was the value would have been exefile and not secfile. So what happens is Windows now checks the .exe key and sees secfile value, this points to the secfile key where is sees Application value which finally points to the exefile key in HKEY_LOCAL_MACHINE.

[HKEY_CURRENT_USER\Software\Classes\.exe]
@=”secfile”

points to . . .
           
[HKEY_CURRENT_USER\Software\Classes\secfile]
@=”Application”

which points to . . .

[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\exefile]
@=”Application”

So in the future if you think your exe association has been hijacked first area to check the .exe key in the registry and go from there. On a Windows XP machine by default HKEY_CURRENT_USER will not have an .exe key and only the values below in the HKEY_LOCAL_MACHINE .exe key.

[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.exe]
@=”exefile”
“Content Type”=”application/x-msdownload”

[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.exe\PersistentHandler]
@=”{098f2470-bae0-11cd-b579-08002b30bfeb}”

If you want to test exe hijacking you can save the following lines below in reg file and import it. From their on any executable run will load up Windows Calculator. Once testing is finished you can simply delete the .exe key in HKEY_CURRENT_USER. The same applies in the HKEY_LOCAL_MACHINE but here you cannot delete the .exe key. So if you want to test using HKEY_LOCAL_MACHINE I recommend you backup the .exe key first.

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Classes\.exe]
@=”anything”
[HKEY_CURRENT_USER\Software\Classes\.exe\shell]
[HKEY_CURRENT_USER\Software\Classes\.exe\shell\open]
[HKEY_CURRENT_USER\Software\Classes\.exe\shell\open\command]
@=”\”C:\\windows\\system32\\calc.exe\””

Reference:

http://www.threatexpert.com/report.aspx?md5=6472e446c64a34edf7fe4ae8270e6faf