http://www.aclu.org/privacy/spying/14891res20011023.htmlWiretaps limited to transactional or addressing information are known as "Pen register/trap and trace" searches (for the devices that were used on telephones to collect telephone numbers).
The requirements for getting a PR/TT warrant are essentially non-existent: the FBI need not show probable cause or even reasonable suspicion of criminal activity. It must only certify to a judge - without having to prove it - that such a warrant would be "relevant" to an ongoing criminal investigation. And the judge does not even have the authority to reject the application.
Pen register searches applied to the Internet
The Patriot Act applies the distinction between transactional and content-oriented wiretaps to the Internet. The problem is that it takes the weak standards for access to transactional data and applies them to communications that are far more than addresses. On an e-mail message, for example, law enforcement has interpreted the "header" of a message to be transactional information accessible with a PR/TT warrant. But in addition to routing information, e-mail headers include the subject line, which is part of the substance of a communication - on a letter, for example, it would clearly be inside the envelope.
The government also argues that the transactional data for Web surfing is a list of the URLs or Web site addresses that a person visits. For example, it might record the fact that they visited "
http://aclu.org" at 1:15 in the afternoon, and then skipped over to "
http://fbi.gov" at 1:30. This claim that URLs are just addressing data breaks down in two different ways:
Web addresses are rich and revealing content. The URLs or "addresses" of the Web pages we read are not really addresses, they are the titles of documents that we download from the Internet. When we "visit" a Web page what we are really doing is downloading that page from the Internet onto our computer, where it is displayed. Therefore, the list of URLs that we visit during a Web session is really a list of the documents we have downloaded - no different from a list of electronic books we might have purchased online. That is much richer information than a simple list of the people we have communicated with; it is intimate information that reveals who we are and what we are thinking about - much more like the content of a phone call than the number dialed. After all, it is often said that reading is a "conversation" with the author.
Web addresses contain communications sent by a surfer. URLs themselves often have content embedded within them. A search on the Google search engine, for example, creates a page with a custom-generated URL that contains material that is clearly private content, such as:
http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=sexual+orientationSimilarly, if I fill out an online form - to purchase goods or register my preferences, for example - those products and preferences will often be identified in the resulting URL.