Hello-
I am writing to tell you a solution to the problem I was having.
Problem:
Threat Detected box would pop up every few minutes (sometimes seconds). Malicious URL Blocked, with various URLs given, and sometimes none at all. Avast scan showed no infection. Malware Bytes scan showed no infection. Avast boot scan found nothing. This problem persisted for many days while I pulled out my hair and Googled for similar conditions. The Threat Detected box would pop up even before my browser (Firefox) was launched. Sometimes I would hear random system “dings” but no message would appear. In hindsight I believe it was the rootkit virus (it turned out to be a rootkit virus) trying to connect with random websites. My computer was also constantly crashing.
Solution:
This forum gave me the answer. On post about a similar problem, someone named Essexboy provided a link to something called TDSSKiller put out by Kaspersky. Here’s a link to that post:
http://forum.avast.com/index.php?topic=83140.15
I downloaded and ran TDSSKiller and it found “Rootkit-boot.pihar.a” It took two restarts to delete it, but now I am having no more popups or crashes. I hope this post helps anyone who might be in a predicament similar to the one in which I recently found myself.