Windows Explorer provides a way to hide a file s extension in Windows Explorer. Virus writers use this feature to disguise executable files as something more innocuous, such as text files. By changing the appearance of a malicious executable’s icon, malware authors have a much easier time convincing users to run malicious software using social engineering techniques, F-Secure s Mikko Hypponen explains in a blog post [f-secure.com]. Read the full story here: http://www.f-Secure.com/.
Source: https://threatpost.com/windows-7-retains-windows-explorer-security-risk-050509/72615/