Original URL: http://www.theregister.co.uk/2009/05/06/win7_hacker_risk_fail/

Win 7 RC fails to thwart well-known hacker risk

Malware extension renaming ruse stays undead

By John Leyden

Posted in Security, 6th May 2009 10:26 GMT

An almost-ready version of Windows 7 retains a feature from Windows NT which expedites a well-known hacker trick, according to net security experts.

Win 7 RC omits a fix for a long-standing security shortcoming in Windows Explorer. As with previous versions of Windows, dating all the way back to windows NT, the version of Windows Explorer in Win 7 hides the extensions of known file types.

This is a potential problem, because virus writers abuse this feature in attempts to disguise executables as document files. For example, if VIRUS.EXE is renamed as VIRUS.TXT.EXE or VIRUS.JPG.EXE, then Windows hides the .EXE part of the filename. VXers also routinely change the icon inside the executable to resemble the icon of a text file or an image, further disguising a trap that has caught the unwary time and time again.

Net security firm F-secure reports that Win 7 RC allows this trickery to continue. A blog posting by F-secure on the problem, complete with screenshots, can be found here.

It is possible that Microsoft will thwart this particular social engineering trick, once the full version of the software becomes available in late October, or thereabouts. Redmond has already disabled the Autoplay functionality in Win 7 by default, thwarting a technology that meant malware-infected USB sticks and the like infected machines they were subsequently plugged into with minimal user involvement. The functionality was notoriously exploited by the prolific Conficker superworm, to cite just one example.

Demand for downloads of Win 7 RC has been high since its release on Tuesday. Surfers looking to get the software from alternative sources are advised to tread carefully, following reports that links to some supposed unofficial download sites actually point to websites harbouring exploit code and malware. ®