dstates writes "The Washington Post is reporting that some Internet Service Providers (ISP) have been using deep-packet inspection to spy on the communications of more than 100,000 US customers. Deep packet inspection allows the ISP to read the content of communications including every Web page visited, every e-mail sent and every search entered, in short every click and keystroke that comes down the line. The companies involved assert that customers' privacy is protected because no personally identifying details are released, but they make money from advertisers who use the information to target their online pitches. Deep packet inspection is a significant expansion over tools like cookies in the ability to track a user. Critics liken it to a phone company listening in on conversations."