It is the surely the first security demonstration in history to draw inspiration from a notorious 1970s porn flick and a more recent Brad Pitt film, based on the underground bare-knuckle fighting scene.

U.S. open source security outfit Untangle is to run a public test of six of the most popular anti-porn filters at next week's RSA Show in San Francisco, dubbing the head-to-head as the Deep Throat Fight Club in a disturbing metaphoric fusion of sex, violence and open source developer zeal.

For the filtering contestants involved - Barracuda, Fortinet, ScanSafe, Sonicwall, WatchGuard and Websense - the title is probably about right. The potential for embarrassment is huge and it could get bloody. Do much-vaunted porn filters actually work as advertised?

"No filter is going to catch everything," admitted Untangle's CTO and appropriately-named co-founder, Dirk Morris. "So we're benchmarking the industry to give everyone a better idea of what to expect."

No details were offered of what methodology would be used beyond the general comment that the Deep Throat Fight Club would "mimic real-world scenarios in a live and fully transparent test."

The company will obviously foreground its own filtering systems although it is worth pointing out that Untangle does not itself sell comprehensive anti-porn blocking, relying instead on blocking of certain types of domain.

Content-based anti-porn filtering has a mixed press. Some rate it as too complex and expensive for what it delivers. Others prefer to stick to simple URL filtering, blocking the potential sources of porn, rather than worrying about whether a particular image or sentence breaches a pre-defined rule.

"Much like blocking spam, porn filtering is a difficult moving target. New porn sites spring up everyday. We've come to accept that some spam will get through email filters, but is that acceptable for porn in schools? Is blocking 80 percent, 90 percent or 95 percent acceptable for businesses or public libraries?, asks Untangle in its official release.

Untangle ran a similar test on anti-virus software at last August's LinuxWorld Show under the title "Anti-Virus Fight Club." The results of that contest can be found on Untangle's Web site.