National Security Agency

In popular culture, the NSA is often portrayed dealing with human-source information (spies) but this rarely actually occurs and such actions are usually left to other agencies. In the past, NSA did not even want to know what the other agencies were doing (many in the NSA still don't want to know). The vast majority of the agency is geeks with electronics that never stray far from their tinted window facilities. Also, they are depicted as staging clandestine operations within the US. This is not only rare, it is illegal and historically the NSA has been extremely careful not to do anything that even suggest such actions. The NSA was created to deal only with foreign intelligence (even before it was named "NSA"). Legally they cannot collect, disseminate, process, etc., any information from the USA or of citizens therein. However, some mostly isolated cases of domestic operations have happened. Notably, anti-Vietnam war activists, journalists, athletes, and civil-rights activists (mostly ones that criticized the war) were targeted. Initially this was done through a end-round method of establishing operation that could supposedly spy on US citizens without violating the law. Despite the loophole threading, it was most likely illegal. Authorities within the NSA itself were responsible for stopping the operation and chastising those involved before anyone outside the NSA knew about it (except for a few of the targets who discovered they'd been spied upon). But, some USA citizens still continued to have their international communications monitored. This was probably legal (originated outside the USA), but still, many within the organisation objected and the possibility of inadvertently acquiring entirely domestic information (a blatant violation) was a danger although most of the info came from British intelligence which greatly minimized the chance. The NSA ceased targeting of US citizens no mater where they were or where they spoke to. Later, in the wake of abuses by many other government agencies discovered in the fallout of the Watergate scandal, the NSA's history of these illegal and just short of illegal operations were discovered and prompted the Foreign Intelligence Surveillance Act of 1978 to codify the bounds for the US government operations (which restricted some agencies but actually didn't change anything the NSA could do up to that point. But it would restrict something they would do later). After the Twin Towers were destroyed, laws changed and intelligence agencies arranged to cooperate and share more readily. This lead to agencies asking each other to do things each were not legally allowed to do themselves. The CIA wanted to collect and electronically sort out all communication that might originate with terrorists. They got computer software from a 3rd party and then gave it to the NSA to tap over 17 thousand lines of communication. Note, even under the 1978 restrictions, they could tap international lines. But, the software didn't know the rules (and probably couldn't), and collected everything (legal and illegal info). The CIA could plausibly feign ignorance about how the software worked and probably didn't violate any laws by providing the people to be targeted (under CIA rules). There were certainly people on the list that the NSA could not legally target, but that was supposedly the CIA's responsibility, as was the actions of software, they were just cooperating as they had been ordered to do by their superiors at the executive branch. But, as has always been the case at the NSA, people started questioning if everything was legit. It was discovered by the NSA that their were illegal targets is (for the NSA) on the list and it was collecting illegal information even from legal targets. The protests went up the chain of command but return responses basically were 'just cooperate and keep fighting terrorists'. many people at the NSA would not let the situation continue, protests began to bypass the chain of command and there were even secret lawsuits filed by employees against their superiors charging them with illegal spying. When nothing changed, some top level official resigned in protest and out of self defense (the if president himself orders a law broken, any who follow that order are legally at fault). Sadly, things continued as they were. Until a subcontracted outsider, Edward Snowden, when public with evidence of these goings on that he'd collected over a long period. One thing that the evidence clearly shows is that people at the NSA went above and beyond to try and stop the illegal activity. This situation, as of 2015, still remains unresolved.

One final note, while the NSA rarely engages in foreign clandestine operations, they are fully authorized to do so. Sometimes bugs have to be physically placed, alarms disables, sites broken into, security guards drugged, etc...