Single code typo triggers massive Internet Explorer hack attacks

A single typo - an errant "&" character in Microsoft's development code - was the bug that let hackers ruthlessly exploit Internet Explorer since early July.
8/4/2009 4:00:00 AM By: Gregg Keizer

Microsoft yesterday confirmed that a single superfluous character in its own development code is responsible for the bug that has let hackers exploit Internet Explorer (IE) since early July.

A pair of German researchers who analyzed a vulnerability in a Microsoft-made ActiveX control came to the same conclusion three weeks ago.

"The bug is simply a typo," Michael Howard, a principal security program manager in Microsoft's security engineering and communications group, said in a post Tuesday to the Security Development Lifecycle (SDL) blog. Howard, who is probably best known for co-authoring Writing Secure Code, went on to say that the typo -- an errant "&" character -- is the "core issue" in the MSVidCtl ActiveX control.

That video-streaming control was created by Microsoft using a modified version of an older edition of a code "library," dubbed Active Template Library (ATL), that Microsoft admitted Tuesday contained multiple vulnerabilities. Also on Tuesday, Microsoft patched Visual Studio, the company's development platform that contains ATL. Those patches, however, do not automatically fix software that was developed using the buggy ATL. Instead, vendors -- Microsoft as well as third-party firms -- must use the patched Visual Studio to recompile their code, then distribute the new, secure software to users.

Howard said that the bug in the MSVidCtl ActiveX control was introduced by an internal version of ATL, not one that was available to outside developers.

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