BT to trial behavioural ad system Phorm

The trial is set to start soon and will involve almost 10,000 BT broadband customers, with the Phorm system re-branded as 'Webwise'.

Phorm tracks users' behaviour across multiple websites. It is designed to make online ads more relevant by taking account of all the websites a person visits during a complete 'browsing session', rather than just the content of a single web page.

For example, if a user visited five golfing websites before visiting a financial services page, the technology might suggest serving another golf advert on the financial page, where typically an advert for a financial product might have appeared.

BT said it is using the trial to see if the system can cope with large numbers of users, and to test their reactions. The test will run over the summer. Rival ISPs TalkTalk and Virgin are both also considering using Phorm.

However, privacy campaigners and some users are unhappy with Phorm, as it uses people's web-surfing history and habits to target them with adverts.

In  April, The Foundation for Information Policy Research (FIPR), a group of Cambridge academics, said the service infringed users' privacy and branded the system 'illegal'.

The FIPR said that gathering information about website visits without the user's consent amounted to a breach of the Regulation of Investigatory Powers Act, which prevents unlawful interceptions of communications.

In a statement, the FIPR said:"Users should have to opt in to such a system, not merely be given an opportunity to opt out. Failure to establish a clear and transparent 'opt-in' system is likely to render the entire process illegal and open to challenge in UK and European courts."

Phorm works by assigning the computer of each internet user a number, so that the path of the user across the internet can be tracked.

The company said that individual websites may hold registration details about their own users, but they are unlikely to know which other websites and services they use. Such information is typically known only by the ISP.

Once the advertiser's criteria are satisfied, the advert is served and the details of that person's path across the internet are deleted, Phorm said.