In a letter to a congressional committee, AT&T said it is "carefully considering" monitoring how its users surf the Web. In a similiar letter, Internet service provider Charter Communication said it had plans to do the same. ISPs Bresnan Communications, CableOne, CenturyTell, Embarq, Knology and Wow already track their users' activities on the Web, according to Silicon Alley Insider, which put together a list of ISPs and portals that do and do not track users.