Anti virus software for the 64-bit version of Windows Vista is struggling to properly protect the operating system, according to a new test by the Virus Bulletin security certification body.

Of the 20 anti-virus product tested, 35 per cent failed to meet the test’s criteria. Six of the failing grades were caused by so called false positives, legitimate files that are incorrectly flagged as malware.

Of the major vendors, McAfee Virusscan and Symantec Antivirus both passed the test, as did Microsoft’s Forefront, Redmond’s enterprise grade security suite that was released last May.

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