An internal British Telecom report on a secret trial of an ISP eavesdropping and advertising technology found that the system crashed some unsuspecting users' browsers, and a small percentage of the 18,000 broadband customers under surveillance believed they'd been infected with adware.
The January 2007 report (.pdf) -- published Thursday by the whistle blowing site Wikileaks -- demonstrates the� hazards broadband customers face when an ISP tampers with raw internet traffic for its own profit. The leak comes just weeks after U.S. broadband provider Charter Communications told users it would be testing a technology similar to what's described in the BT document.

Leaked Report: ISP Secretly Added Spy Code To Web Sessions, Crashing Browsers | Threat Level from Wired.com