British Telecom, also known as BT, kick started the much-delayed ISP-based behavioral targeting, using Phorm’s ad-serving technology, in an optional based test.

Over 10,000 customers have been invited randomly to participate in the trial when they start their browsing session, said BT.

Concerns over privacy threats continues to loom over such kind of behavioral targeting tests and therefore the European Commission is waging investigations to assess such tests.

The behavioral targeting represents BT’s third such test, but the first one with users opting in voluntarily.