Earlier this month, privacy advocacy group the Center for Democracy and Technology released a report suggesting NebuAd's practice may be illegal under some state wiretap laws. In June, privacy advocates Public Knowledge and Free Press released their own report suggesting that NebuAd hijacks browsers, employs man-in-the-middle attacks, uses packet forgery and installs unwanted cookies in order to track users' Internet habits.
NebuAd has disputed the information in those reports. NebuAd collects limited information about users and it anonymizes the data it collects, company CEO Robert Dykes told a U.S. Senate committee last week. "No one, not even the government, can determine the identity of our users," he said.
Markey and Barton wrote a similar letter in May to Charter Communications, after the St. Louis cable broadband provider announced plans to test the NebuAd system. Last month, Charter announced it was suspending its plans to test the NebuAd product because of customer privacy concerns.