An exploit for a known flaw in Internet Explorer has been published on the web.

The code, which was posted to the web site, exploits a recently patched flaw in Microsoft's browser. It could be used to run unauthorised software on a computer that was not updated with the latest Microsoft patches, security experts warned.

The vulnerability was discovered by security researcher HD Moore who posted code last July that could be used to crash the browser. Microsoft patched it in February, but some security researchers say that it will get more attention from criminals because of this latest exploit code.

"This type of vulnerability has been very popular with malicious attacks in the past and we expect to see its usage increase substantially, now that exploit code is publicly available," security vendor Websense warned.

Researchers at eEye said the Milw0rm code works on IE6, but not on IE7.

"We've tested it against IE 7 and haven't got it to work yet," said Andre Protas, director of eEye's Preview research service.

Protas said that more reliable exploit code likely will be published in the future.