Catherine Herridge tells us this: FBI using elite surveillance teams to track at least 48 high risk ISIS suspects. To wit:
With at least a dozen agents assigned to each case, providing 24/7 coverage, this high level of surveillance reflects the severe risk associated with suspects most likely to attempt copycat attacks after Paris.
“There is a very significant number of people that are on suspicious watch lists, under surveillance," Republican Sen. Dan Coats said.
Coats, who sits on the Select Committee on Intelligence, would not comment on specifics, but said the around-the-clock surveillance is a major commitment for the bureau. "The FBI together with law enforcement agencies across the country are engaged in this. It takes enormous amount of manpower to do this on a 24-7 basis. It takes enormous amount of money to do this," Coats explained.
Did Coats leak this information or merely confirm it? And does it compromise the investigations with the subjects? One would think that knowing there are 48 people being survielled might raise some suspicion among those being surveilled.
He/she might use extra precautions when attempting to communicate with comrades -- using burner phones, for one, destroying the chips after each use. They certainly wouldn't use email in a way that would likely be intercepted.
When leaving home they might wear a bright colored shirt with a couple of changes on underneath. Altering the manner in which they walk is another way that might throw off followers.
Coats said, "It takes enormous amount of money to do this." No doubt it does. We all hope it prevents an attack and isn't merely something that will help lead to arrest after an event occurs.
Meanwhile, here's a 2008 article from NPR which tells us FBI Surveillance Team Reveals Tricks Of The Trade. No high tech stuff there, just old fashioned following.