Microsoft fixes critical flaws

The patches, which carried Microsoft's highest security warning, all are to prevent malicious hackers from remotely taking control of computers without permission.

Three of the patches aim to protect Windows users who unwittingly expose their computers to attack by visiting web pages infected with malicious code, or look at similarly tainted e-mails with Outlook Express or Windows Mail. A fourth patch prevents hackers from gaining remote access to PCs by installing a specially crafted program.

Two of these critical updates fix holes in the company's newest operating system, Windows Vista, which Microsoft has touted as the most secure ever.

Vista went on sale to consumers at the end of January; in April, Microsoft broke its once-monthly update schedule with an emergency fix after the company and security experts found hackers were exploiting a hole in the way Vista and other versions of Windows handle animated cursor files.

Microsoft also on Tuesday released a patch for its Visio diagram drawing program and a patch for a vulnerability in Windows that could allow unauthorised users to break into computers to steal passwords and other user information.

Additionally, Microsoft released seven non-security, high-priority updates on Tuesday, including a monthly update to a tool that removes harmful software from PCs.

On the second Tuesday of each month, the Redmond, Washington-based software maker releases security updates. Windows users can download patches from Microsoft's website or get them through an automatic update system.

Spammers are taking advantage of "Patch Tuesday" to send e-mails that appear to come from Microsoft, but that actually install programs that let hackers gain future access to infected PCs.

Fred Touchette, a security analyst for the spam and virus filtering company AppRiver LLC, said he has seen this particular tactic twice before, most recently in 2004. The current attack, which started late last week, is "pretty small," he said.