Microsoft warns of major Patch Tuesday update

Covers 25 flaws, five rated 'critical'.

Microsoft has released its advanced notification for April's Patch Tuesday update, which will address 25 problems in 11 security bulletins.

Five of the vulnerabilities are rated 'critical', and apply to enterprise applications including Microsoft Office and Exchange. Affected operating systems include Windows 2000, XP, Vista, 2003, 2008 and Windows 7.

The critical flaws could allow a remote attacker to take control of a machine, install malicious software, or contribute to a denial-of-service attack.

Alan Bentley, vice president at security firm Lumension, urged IT departments to prepare for the patches well in advance.

"IT departments will have to address and patch almost every endpoint in the organisation, including servers, laptops and desktops," he said.

"They should plan ahead as to how they are going to test and then deploy these patches with minimal interruptions to employee productivity."

Wolfgang Kandek, chief technology officer at vulnerability management firm Qualys, agreed that this month's large security update will keep system administrators busy.

"An attacker can use these vulnerabilities to remotely execute code on the victim's machine, and they should be addressed as quickly as possible," he said.

However, Kandek added that Windows 7 has been left relatively unpatched, suggesting that it is a more secure platform that previous releases.

"Windows 7 has fewer critical updates to install than the older operating system versions, an indication that the newer version of Windows is more robust and secure out of the box," he said.

Many of the fixes require a system restart, according to Microsoft, and just one earns the lowly rating of 'moderate'.

One of the problems likely to be patched is the F1 key issue reported earlier this year that affects Internet Explorer.