Has the US government ever been caught or accused of hacking?

Answer 1

For the purposes of this question, the term "hacking" will be interpreted to refer to accessing a computer system by circumventing its security system.

Different entities of the US government have been accusedof hacking - for example Iran accused the US of being behind the Stuxnet worm that attacked the control systems of the centrifuges they are using to produce high purity nuclear materials for their nuclear program. The only publicly confirmed instances are related to legal wiretaps granted by judges pursuant to investigations of known or suspected terrorists and other criminals.