Microsoft security teams have struck what they hope is a fatal blow at Srizbi, the once-powerful spam botnet that has been fighting for its life since last year's demise of two US-based network providers that offered vital lifelines.

The company's Malicious Software Removal Tool has already proved invaluable in mass disinfections of major pests. In October, for instance, it went after Rustock, another large botnet used to relay spam through hundreds of thousands of infected machines.

"We hope to make a positive impact with the addition of Win32/Srizbi into MSRT," Microsoft's Vincent Tiu writes.

This month's MSRT was unleashed on Tuesday, the same day Redmond released patches fixing security vulnerabilities in four of its products. Microsoft warned that "consistent exploit code" for critical remote execution flaws in Internet Explorer was likely, meaning it's probably only a matter of time until attacks in the wild are seen.

The company also plugged critical holes in its Exchange server. Attackers could target the vulnerabilities by sending maliciously crafted emails that caused the machines to shut down or hijacked.

This month's Patch Tuesday also included fixes for less severe vulnerabilities in Microsoft's SQL Server and Office Visio.

For an overview of the patches, head over to this page from Sans.

Not to be outdone, Research in Motion offered a patch for software that allows users to easily install software on their BlackBerry devices. The BlackBerry Application Web Loader suffers from a buffer overflow defect that could allow attackers to remotely install software on a vulnerable system.

Secunia rates the vulnerability "highly critical," the second highest ranking in its five-notch scale. RIM has more about it here. ®

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