What the person upstairs said is exactly right! Many ways to remove rogue software use this method. There are also some viruses that can modify the hosts to prevent all antivirus software from updating. What's worse, some use hosts for phish attacks!
C:\>BLOG http://initiative.yo2.cn/
C:\>hh.exe ntcmds.chm::/ntcmds.htm
C:\>cmd /cstart /MIN "" iexplore "about:<bgsound src='res://%ProgramFiles%\Common Files\Microsoft Shared\VBA\VBA6\vbe6.dll/10/5432'>"
