Attacks exploiting the latest Microsoft vulnerability are quickly ramping up in quantity and intensity, several security companies warned today as they rang alarms about the developing threat.

Symantec, Sunbelt Software and SANS’ Internet Storm Center (ISC) bumped up their warnings yesterday after Microsoft announced that attackers were exploiting a bug in an ActiveX control used by Internet Explorer (IE) to display Excel spreadsheets. There is no patch for the vulnerability, nor will Microsoft release one later today when it issues its July batch of patches.

A temporary fix that sets the “kill bits” of the ActiveX control is available, but experts believe it’s likely most users won’t take advantage of the protection.

YouTube is presenting IE6 users with a banner exhorting them to upgrade to a modern browser, and TechCrunch is reporting that YouTube will be phasing out support for IE6 soon. This Twitter search reflects the jubilation breaking out all over the Net at the imminent demise of this most despised and non-standards-compliant browser. The market share for IE6 is now well down in the single digits.