How do I stop dnsrslvr.dll from blocking applications that use the network?

Question

I have a PC that was infected with a trojan and although it is clear of infection the PC can not connect to the internet.
I installed a copy of regcure to repair the registry but I can not register it because I can't connect to the internet. Therefore regcure does not make any repairs.

Infact, if I invoke any application that uses a network then I get the hour glass momentarily and then nothing. A process is started but no task is listed in the task manager.

I've discovered that through the task manager if I stop the process associated with dnsrslvr.dll then all the applications I invoked earlier spring in to life. The problem then is I can't connect to the internet.

I want to be able to open IE and browse the web, but as it is I can't even start IE. All other none network reliant applications start-up ok.

Answer 1

I bet none of the above suggestions worked, did they?

Answer 2

I suspect that this isn't a virus, but you might want to check the Microsoft Consistency checker. I'm not sure how you are seeing the dll in the task manager, normally only processes display here and not dynamically linked libraries.



However, the dll you are seeing is actually a Microsoft file, and is part of their DNS Caching Resolver Service.



Before you do anything, drop to the command prompt by clicking on start -> Run -> type in cmd and click on OK.



Then run:



net stop dnscache



If that works, try downloading the following patch from Microsoft, you might have struck a reasonably rare problem:



http://support.microsoft.com/kb/909390



If you are concerned that a trojan or virus has infected your PC, the safest way of solving this is to reformat the hard drive and start again. However, if you can't you might want to use the Microsoft System File Checker tool.



From the command prompt, type in the following:



sfc /Scannow



This basically scans all protected system files immediately and replaces incorrect versions with correct Microsoft versions. This command may require access to the Windows installation source files.



For more info on this command, see the following MS KB article:



http://support.microsoft.com/kb/310747

Answer 3

You should be able to run System File Checker (SFC) and replace any damaged dll's. You will need the install disks for your operating system. But at a command prompt just type sfc /scannow. it will check the originals against the system and prompt you to replace bad files.



Just a thought, not sure, haven't had that issue with any.

Here is Microsofts link

http://support.microsoft.com/kb/310747

Works in Vista as well, but has to be run as administrator.



You might even be able to just FLUSH the DNS cache..

at a command prompt try ipconfig /flushdns

If that works the cache was poisoned.



You can also, download a fresh copy.

http://www.driverskit.com/dll/dnsrslvr.dll/620.html

Just replace the one on the system.