Fortinet detected 97.7 percent in the main porn-blocking test, while Watchguard detected 97.3 percent, Websense detected 97 percent, SonicWall detected 96.1 percent and Barracuda detected 94 percent.
Fortinet also led in the porn-categorization test, which measured performance against a human's judgments.
Not all participants were pleased with the outcome. Watchguard has questioned the test's methodology, arguing that URL filtering can be circumvented in a number of ways, including using short URLs and website proxying.
Untangle's tests for the "Deep Throat Fight Club" were based on searching 50 porn terms, then choosing those that were 100 links deep and using them to measure the filters. The products were graded against a human making the same judgments.
The full list of sites tested is included in a downloadable spreadsheet at Untangle.com.
"If you are expecting to block all porn, all these products will not be effective," Dirk Morris of Untangle wrote in a post-test blog. "However, if you're looking to control and monitor porn usage as much as possible, these products make great candidates."