BT should face prosecution for its "illegal" trials of a
controversial ad-serving technology, a leading computer security
researcher has said.

Dr Richard Clayton at the University of Cambridge made his comments after reviewing a leaked BT internal report.

The document reveals details of a 2006 BT trial with the Phorm system, which matches adverts to users' web habits

"It's against the law of the land, we must now expect to see a prosecution," he told BBC News.

But BT plans to push ahead with a further trial of the technology later this summer, the BBC has learnt.

"We have not announced a date yet; we are still planning - it will be quite soon," a spokesperson told BBC News.

Revelations about earlier trials have prompted some customers to
organise protests in London to coincide with BT's AGM on 16 July.

'Small test'

The company did not inform customers that they were part of the
original tests in 2006 and 2007, although 30,000 subscribers were
involved.

Nearly 19m web pages were intercepted during the 2006 tests, according
to the leaked report, posted to the whistle-blowing website wikileaks.

BT described it as "a small scale technical test".

During the trials adverts were stripped out of web pages served up to
BT customers and replaced with more targeted ads, if available.

If none were available, adverts for one of three charities were inserted.

The report also reveals that BT believes that a large scale deployment of Phorm would be "operationally challenging".

It projected that it would require as many as 300 servers to roll out
for all BT customers and added that BT was "unable to find hosting
accommodation that will enable a deployment of this model".

However, the BBC now understands that the technology behind Phorm has
been updated and large scale trials are much more feasible.

'Illegal trial'

Dr Clayton said the leaked report "clearly shows that back in 2006 BT
illegally intercepted their customers' web traffic, and illegally
processed their personal data."

He continued: "The BT author seems delighted that only 15-20 people
noticed this was happening and looks forward to a new system that will
be completely invisible.

"This isn't how we expect ISPs to treat their customers' private
communications and since, not surprisingly, it's against the law of the
land, we must now expect to see a prosecution."

He said that the BT report also noted that "communications regarding
advertisement systems and information collection could lead to negative
perception if not carefully handled".

"They seem to have failed in this aspect as well," he said.

BT said it did not want to comment on Dr Clayton's remarks.