Criminal justice gags are usually hours to days depending on the case.

The longer ones are usually to protect the arrestee if they are being put into protective custody / witness protection or are released as an informant.

Since this is national security related who knows, I don't even know if these cases have been brought up to the supreme court before.

Yes, unsurprisingly there is an enormous amount of case law on this topic.

https://en.wikipedia.org/wiki/Habeas_corpus_in_the_United_St...

if its a computer access break-in FED law states 90 days notice..while not directly applying it would seem if someone was caught on illegal access after 90 days FEDs would have to let both the criminal know and theri lawyer so arrest would no longer be secret at thatpoint.