Anti-virus firm Sophos yesterday suspended detection of a "porn dialler application", following complaints from its UK-based developer.

A Sophos spokeswoman confirmed that it had removed detection of the Coulomb dialler yesterday afternoon on legal advice, following representations from Coulomb Ltd. Sophos is investigating if its AV software is wrongly detecting a legitimate dialler application developed by Coulomb Ltd as a Trojan.

In the meantime, Sophos has suspended detection of the Coulomb dialler, which remains designated as malware by several AV firms. Resellers and end users who notified The Register of the issue question Sophos’ actions. One end user described Sophos as "wimps" for "backing down in the face of cartoony [shallow legal] threats".

Porn diallers are often written to change a user's dial up settings to ring premium rate or overseas phone numbers without the informed content of consumers. It's only when a user is landed with a huge bill that they realise something is amiss.

Informed consent

But Coulomb Ltd said this was not how its application worked. David Knell, chief exec of Coulomb Ltd, said its application did "exactly what it says on the tin". Its dialler is offered as a payment option on various adult entertainment (sex) websites. If users download the software they are informed that they are to be transferred onto a premium rate number for the duration of a session. This spending limit is capped at £20 per session in line with recommendations from premium rate regulator ICSTIS, Knell says.

"This is no more a Trojan horse than a big wooden horse with a sign 'Greek Soldiers Inside'" Knell said.

He acknowledged that various AV scanners flagged up the firm's application as illicit. He said that he had begun discussions with Sophos about the issue first because "it had to start somewhere". "We may well contact others later," he added.

Sophos specialises in the enterprise market. Resellers who notified us of the issue question how it could ever be legitimate to run Coulomb's application from a corporate PC

"I'm pretty disappointed that the latest virus detection release (IDE in Sophos terms) has been butchered to remove the detection of Coulomb's diallers," one reseller writes. "In my experience: Coulomb dialler = porn dialler. Sophos is used in networks - network users should never have a reason to download a dialler."

The designation of malware, once clear cut, has become more contentious over the last year or so. Alex Shipp, senior AV technologist at MessageLabs, which uses a number of third-party AV scanners in its email filtering service, said that AV companies such as McAfee that offer end users more choice over what application to block were in a better position than Sophos to withstand legal pressure. ®

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