Good social engineering can threaten users more than a serious software flaw, Microsoft's Anti-Malware Engineering Team argued in a blog post on Tuesday.

A relatively unknown worm has spread moderately successfully without exploiting any flaws in the Windows operating system, according to data collected by Microsoft's software for removing malicious code. The virus--known as Alcra or Alcan--spreads through popular peer-to-peer file-sharing systems by offering itself up using the names of popular files on program cracking sites. The social engineering has been quite successful: During February, about 250,000 machines had been infected by the program, according to data collected by Microsoft's Malicious Software Removal Tool.
SecurityFocus