What type of intelligence operations should the government be allowed to use for national security? [View all]

Recent events have shown that many on the board have a problem with the government use of phone data (phone calls, lengths of time of calls, etc) used for national security reasons. This is despite the fact that the data was attained by a warrant and any other use of the data would require further court approval. To me, that seems like a pretty good balance, at least when it comes to National security.

So the question is,if this is a problem, what should the government be allowed to do when it comes to national security?