There is a very good chance that you’ve become infected with a very elusive type of virus – the rootkit. The symptoms you’ve described lead me to believe that you’ve become infected with a new type of rootkit known as TDSS. It also goes by the name of TDL1, TDL2, TDL3 (on 64bit systems), Alureon or Tidserv. While the name changes depending on the antivirus scanner, the infection is the same and causes quite a few problems. Most notably, TDSS will redirect your browser away from legitimate websites and towards malicious websites attempting to install other various trojan infections.
Rootkits are also obnoxious for their inability to be detected by most virus scanners. Many antivirus companies have received complaints over the years for how slow and clunky they are. In effort to remedy the stereotype of degrading system performance, most antivirus applications are now tailored to run as fast as possible while using as few system resources as possible. Although this does dramatically increase the end-user experience, it also prevents these scanners from running deep heuristic scans, checking inside of archives and scanning for rootkits.
Luckily, detection and removal of TDSS is quite simple. Kaspersky Labs offers a free utility for discovering and eradicating TDSS rootkits.
If this fails to fix the problem, you may have a different type of infection. There are several utilities available for free online to combat malicious infections, but I would recommend you visit a qualified technician to help you remedy the problem. Most of the tool that technicians utilize can cause vast amounts of irreparable damage if used incorrectly.
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