
Security vendors have seen series of targeted attacks that used malformed .ani files. The flaw allows attacks to take over control of a system without any user interaction.
The attack is launched when the user receives a specially-crafted .ani file embedded in either a web page or e-mail message. The file is installed on the user's system and then delivers its malicious payload.
Nearly all supported versions of Windows and Internet Explorer are vulnerable to the attack. Only users running Windows Vista and Internet Explorer 7 in protected mode appear to be safe, said Microsoft. In protected mode, no file is allowed to access or modify any system files without user permission.
Alternative browsers such as Firefox or Opera do not appear to be vulnerable to the attack.