I just read Betty Medsger's "The Burglary," about the burglary of the Media, PA office of the FBI in 1971 by a group of people who named themselves the Citizens Committee to Investigate the FBI. J. Edgar Hoover went apoplectic over it, but they never found the burglars. The documents stolen led to the revelation of COINTELPRO, among many other things. The book is also a primer on the history of 20th century surveillance by our government.
A band of rabid communists isn't going to have millions or billions to spend undermining our democracy - such as it is - but the FBI and the NSA do.
So, yeah, I wouldn't worry about those commies ... if there are any left.