Mass surveillance is out of control as you say, and I am a strong proponent of reigning in warrantless wiretaps and governmental overreach. However, as many people have stated, a pen register (which requires a warrant) against a specific individual suspected of a crime where there is a MASSIVE amount of evidence suggesting that the suspect is guilty has nothing to do with mass surveillance. This is targeted, narrowly scoped surveillance of a specific suspect and is precisely what law enforcement should be doing.