DNS settings hijacked and av.exe won’t go away. Internet turns Inertnet!

Had a fun time today cleaning off some trojans and rootkits.  On this one client system, while trying to go online, the Internet  turned into the Inertnet! (Hahahha! I love that one!)  As usual, I have lots of ideas why, but no real evidence and clients saying “I don’t know how it got there.”  Doesn’t really matter though, it’s there and I am going to clean it off.  I managed to easily scan for and clean off a couple of them, but one would’t detect with any scanner.  AV.exe kept popping up, showing the fake windows security center and Antivirus 2010.  I used Process Explorer to see the offender, but I couldn’t find the file, it was hidden.

I rebooted with UBCD4Win, found the file and deleted it.  Problem is, this caused a mess in Windows. Nothing would load, I always got a “Open With” dialog box.  After some Googling, I found out where to fix that in HKCR in the registry.  In there, there was a setting for .exe files to open, and it was set to use av.exe in the user profile to open them!  How do you like that?!!

I wasn’t able to fix that in the current user profile, it was locked down somehow.  Opening in the Administrator account of XP allowed me to fix it though.  The default value for “exefile” should be set to:

“%1” %*

(Just google that for more info.)

Ok, so got that all fixed.  Fun how you clean off these bugs, only to leave windows all messed up after!  Next, did all my final scans, tweaks and other items. (lock down IE, disable scripts/Flash/Adobe, add a windows update to Trusted Sites, and force user to use Firefox.  I also changed the icon on Firefox to the one for IE so the user will pretty much always use it!)  Then I tried to get all the updates caught up, only no go!  Wait, I am on the same Internet connection as my system, and it works for me, why not the client system?  Hmm… well they are on an isolated subnet, going through the firewall separately. (keeps their bugs off my systems!)  But, wait, those are the same DNS settings?

AH! Take a look at those NIC properties in XP.  DNS is hard set to 93.188.x.x!  Nslookup shows that as some place at a .com.ua domain. Well, let’s fix that one, and set to DHCP like it should be!  Problem solved, Windows Update works!

Fun stuff!  I’ve cleaned a lot of bugs over the years, and I’ve heard of DNS hijacking, but that’s the first one I’ve seen like that.