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Slideshow: 10 Massive Security Breaches

"The Microsoft Safety and Security Center has become a hot bed of porn redirects, and sleazy porn sites invariably lead to malware," said Alex Eckelberry, the vice president and general manager of GFI's security division, in a blog post, after spotting the attack on Friday.

Blackhat search engine optimization (SEO), also known as search poisoning, involves filling search results at sites such as Google, Yahoo, or Microsoft Bing with fake results that link to advertisements or malware. Such attacks aren't anything new. In fact, while results vary by search term, according to one study, about 22% of current news searches, as well as searches for "objectionable content," return links to poisoned or infected websites.

But this attack was different, because it only returned poisoned search results for very specific terms. Furthermore, it managed to do this from within the Microsoft Safety and Security Center's own search engine results. "Pretty tricky and impressive," said Eckelberry.

As far as website exploits go, returning adult content via the Microsoft Safety and Security Center search results scores obvious points for irony. In another Microsoft-related twist, Eckelberry said that some search results were also pushing Zugo, "a Bing-branded search toolbar with a history of being installed through exploits and other misleading/deceptive means."

By Saturday, Microsoft had disabled searching on the affected site, which it restored on Monday, after fixing the issue.

Microsoft confirmed that its site had been hacked. "On July 8, 2011, Microsoft became aware of a search poisoning issue affecting Microsoft search users on the Safety & Security Center site. Microsoft quickly removed the search tool and resolved the issue," Bryan Nairn, senior manager for Trustworthy Computing at Microsoft, said via email. "The search tool has since been re-enabled. We apologize for any inconvenience this may have caused for visitors to the website."

Interestingly, the Microsoft search result poisoning exploit came just days after John Howie, senior director of online services security and compliance governance at Microsoft, told Britain's Computing magazine that unlike RSA or Sony, Microsoft was extremely unlikely to be hacked by an advanced threat. "Sony was brought down because it didn't patch its servers, it ran out of date software, and it coded badly. These are rookie mistakes," said Howie. He likewise labeled RSA being exploited by a social engineering attack as a "rookie mistake."

The Microsoft Safety and Security Center attack, of course, rates as little more than a nuisance and, according to Eckelberry, may have somehow involved the site's ability to share search results via Twitter, which hardly seems to qualify as a rookie mistake. Still, was the timing of the exploit coincidental?