Respected malware testing organization, Virus Bulletin (VB), is to offer a new set of tests to rate the effectiveness of antispam products.

The U.K.-based outfit is known for its VB100 certification, awarded to products that can detect 100% of the virus samples from the independently-compiled 'WildList', defined on a rolling basis by the WildList organization.

As VB admits, however, setting up similar tests for antispam products, was always going to be much more difficult.

The methodology the organization has come up with is complex. All the products tested will have to receive exactly the same message stream at the same time, in real time, and the messages received will also have to be real rather than simulated examples. Because such a setup can only hope to approximate the Internet spam load at any one period in time, the volume of email will have to be high enough to make the test realistic.

Another hurdle. Antispam systems typically block some of the messages they receive at SMTP level based on a number of obvious characteristics such as IP address, meaning that these messages will never get as far as the inbox.

Because testers will need to subjectively define whether a message blocked at inbox level was correctly identified or blocked in error, it will be impossible for them to know whether the filter was right or not.

VB claims it has found a way round these and other technical problems that would otherwise skew the results. The end result will be tests that can, VB says, measure spam-catching rates, false positives, and in future possibly also assess performance too, though it has to decide precisely what a product will have to achieve in order to be 'certified'.

According to VB, commercial antispam products will be able to undertake the as-yet unnamed tests for a fee, while free-to-use and open source software will be tested gratis. Preliminary results are expected in February or March. The test spam itself will be gathered using special 'spam traps'.

"We feel strongly that there is a need for a robust and comprehensive anti-spam certification scheme and that our background stands us in good stead to run such a scheme. We are looking forward to publishing the first set of results," said Helen Martin, Editor of Virus Bulletin.