Microsoft has released patches for 23 security holes, 15 of which it has rated critical.
According to security company McAfee, attackers are already exploiting 11 of the vulnerabilities, which affect Outlook, Powerpoint, Internet Explorer and Windows.
Anti-virus company Symantec said it rates the Server Service vulnerability as most critical, followed by the Power Point vulnerabilities.
Kevin Hogan, senior manager, Symantec Security Response, EMEA and JAPAC, said: ?In addition to the PowerPoint vulnerabilities, this month's series of patches includes fixes for issues affecting Internet Explorer, Microsoft Office, PowerPoint, and Outlook Express.
?These vulnerabilities are the primary focus for researchers and attackers alike, and we continue to see an increasing number of content borne threats as a result.
?As desktop applications continue to grow as a target, it is important that users continue to install available updated software patches on all applications regularly.?
Symantec recommends people regularly run Microsoft Update and install the latest security updates, avoid opening unknown or unexpected e-mail attachments or following web links from unknown or unverified sources.
http://update.microsoft.com