National+Security+Letters

What are NSLs?
NSL stands for National Security Letters, which are government mandates requiring the silence of the recipient. The letters entail two different ordinances upon the citizen, first to report all information about customers and their dealing with the business like libraries, banks, internet providers or telephone companies. Second, the letters entail a "gag" provision which requires the recipient to not disclose that they have received a letter or what the letter requested.

Why are NSLs used, and are they legal?
NSLs are used in order to gain legal information and to track possible suspects communication and travel activity. While the information gathered through a NSL is similar to that of a subpoena, the national government uses them in order to gather information before going to a grand jury. Due to the fact that NSLs do not require explicit court approval, the government or FBI may easy find information without disclosing the fact that they are searching. The actual use of NSLs has grown dramatically since the legislation of the USA PATRIOT act has lowered the requirements that the FBI needs for a NSL down to suspicion and the possibility of finding incrimination evidence against a terrorist. However the actual number of NSLs used is hard to track due to the gag provision they entail, the general number of cases grew from just 8,500 before the PATRIOT act to 143,074 after the law was passed.