One of my client had a problem where he couldn’t visit www.hotmail.com and www.yahoo.com. Both sites were timed out after waiting for a long time. He tried loading both sites in Firefox and Internet Explorer and both didn’t work. Other websites loaded fine though. There were other user accounts on his computer and he tried using them. Other accounts were able to load hotmail.com and yahoo.com without a problem. At first, I told him to try clearing the temporary internet files in both browsers but the problem remained.

Flush DNS Cache

Another possible solution was to clear the DNS cache in Windows. So I typed “ipconfig /flushdns” without the quotes in command prompt to flush the cached DNS entries. However, it didn’t stop the problem. Upon further testing with trace route, I found out that the DNS resolution was not a problem. The trace route tests were able to complete successfully. Therefore, the cached DNS entries should be correct.

Double Virus Scanning

As a last resort, I decided to take the hard drive out and scan it with NOD32. Right away, it found about 30 threats and deleted them. I then put the hard drive back and tried visiting www.hotmail.com again with the problematic user account. This time, hotmail.com loaded fine in both Firefox and Internet Explorer. However, yahoo.com was still unavailable. Then I installed avast! 4 Home Edition on the computer and performed another virus scan. It detected a trojan still running in the memory and suggested to restart the computer to do a startup scan. I followed and it removed a couple of trojans. After that, yahoo.com was able to load too.

If your computer has a similar problem where you are not able to access some big sites such as Yahoo, MSN and Google, then it could be affected by a virus or trojan. You should perform virus scan using a few anti-virus software. A last note to make here is that my client already have the AVG Home Edition installed but it didn’t catch the virus or trojan.