BT's covert trial of Phorm's ISP adware technology in summer 2007 involved tracking many thousands more customers without their knowledge than previously reported, it's emerged.

Erroneous reports earlier this month suggested that a total of 36,000 broadband lines had been eavesdropped upon during the two trials. The Register had revealed that 18,000 customers were profiled in 2006, but no figure was released for the second experiment.

Today Phorm said the 2007 trial was actually performed on "tens of thousands" of lines. It refused to provide a specific figure, but at the absolute least there are 38,000 BT Retail customers unaware their communications have been allegedly criminally intercepted in the last two years. The number could be as high as 108,000.

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We asked a Phorm spokesman why it doesn't believe people have the right to know how likely it is they were part of a secret test. "We're just not going to disclose that," he said. "They were BT customers and you have to ask BT about that."

A BT spokesman refused to provide a figure.

Phorms' 2006 financial report, dated 24 April 2007, states that it was about to begin a trial with "hundreds of thousands" of ISP customers. The firm was referring to its second trial with BT, which took place in June of that year, and was immediately denied by the national telco.

Full article here.