Two security organizations have released online tools that let Windows users check for possible infections by Gauss, the newly-revealed cyber surveillance malware thought to have been built by one or more governments.

Kaspersky Lab and the Laboratory of Cryptography and System Security (CrySys) at the Budapest University of Technology and Economics each published Gauss detection tools today.

Gauss, Kaspersky said yesterday, is a sophisticated threat that monitors financial transactions with Middle Eastern banks, perhaps as part of a wider investigation into the funding of terrorist groups. Kaspersky believes that Gauss was built by or under the auspices of a government, in large part because of coding practices that resemble those used in Flame, an advanced spying and data-stealing toolkit that targeted Iranian computers.

Flame, which was uncovered three months ago but may have been operating since mid-2008, was notable for its ability to fake the Windows Update service, then use that to infect up-to-date Windows PCs.

Kaspersky has rejected the idea that Gauss is a run-of-the-mill money-stealing Trojan.

Both CrySys and Kaspersky sniff out Gauss by looking for a custom-built font, dubbed "Palida Narrow," that the malware adds to infected machines.

CrySys first posted a detection tool that relied on the Palida Narrow strategy; Kaspersky took the same approach, but simplified it by inserting an IFRAME element into a Web page. The IFRAME uses JavaScript to check for the presence of the font.

The CrySys tool is available here, while Kaspersky's sniffer can be found here.

CrySys has played a prominent role in analyzing some of the malware that Kaspersky argued is linked to Gauss, including "Duqu," which is believed to have been crafted by the same team that built Stuxnet, the worm used to sabotage Iran's nuclear fuel enrichment program several years ago.

It's not yet clear why Gauss inserts the Palida Narrow font into infected PCs, or what purpose the new font serves. Some have speculated that it may hint at the use of a yet-undiscovered "zero-day" exploit of an unpatched vulnerability in word processing software, such as Microsoft Word.

Yesterday, Kaspersky senior researcher Roel Schouwenberg acknowledged that there are many facets of Gauss that remain mysterious, including whether it, like Stuxnet, relied on one or more unpatched bugs -- "zero days" in security speak -- to compromise personal computers.

Because one payload that Gauss installs is heavily encrypted, Kaspersky and other security firms cannot yet analyze it, and so cannot say whether it exploits unpatched vulnerabilities.

Kaspersky's Gauss infection-detection tool sniffs for the mysterious custom font that the malware installs.

"But I wouldn't be surprised that there is a zero-day [exploit] in that payload," Schouwenberg said in a Thursday interview.

Many antivirus programs, including those from Kaspersky and Symantec, also detect Gauss through their traditional signature-based software.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is gkeizer@computerworld.com.

See more by Gregg Keizer on Computerworld.com.