ISC warned IE users that more widespread attacks are in the offing. "There is some indication that a weaponized exploit may be in broader circulation now, so expect this to ramp up quickly," the group wrote Saturday. "[And] expect Rapid 7 to likely release Metasploit bits in the near term."
Metasploit is an open-source penetration toolkit maintained by Rapid7, another security company. Metasploit typically rolls out exploit modules for new and even unpatched vulnerabilities. Because Metasploit is a resource for both security professionals and cyber criminals, the appearance of an exploit module often results in increased attacks, as the latter seize on the already-built code to launch their own campaigns.
On Sept. 19 -- last Thursday -- HD Moore, the chief security officer of Rapid7 and the creator of Metasploit, said that no exploit module for the IE bug had yet been added to the toolkit.
If attacks do ramp up, Microsoft would be much more likely to issue an "out-of-band" security update to plug the hole. The next regularly-scheduled Patch Tuesday is more than two weeks away, slated for Oct. 8.
However, out-of-band updates from Microsoft are rare: The last one was MS13-008, an emergency patch issued Jan. 14 that dealt with a vulnerability in IE6, IE7 and IE8 that had been exploited for about six weeks.
Users can also temporarily ditch IE for an alternate browser, such as Google's Chrome or Mozilla's Firefox, to stay safe until Microsoft comes up with a permanent fix.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, or subscribe to Gregg's RSS feed . His email address is firstname.lastname@example.org.
Read more about security in Computerworld's Security Topic Center.