Under amendments to the Rules of Federal Criminal Procedure, a judge will now be able to grant an electronic search warrant for a device, even if its location is unknown. Opponents, including major technology firms and digital rights advocates, say the change could lead to unconstitutional searches. Proponents of the change say it is necessary because suspects can hide online or launch cyber-attacks from hundreds of infected computers spread over a wide geographic area.

Ed McAndrew, a former U.S. attorney and cyber-crime specialist in the office of the U.S. Attorney for the District of Delaware, said lawyers could challenge "the scope of the warrant, the amount of information that's seized, the circumstances under which the search is conducted, how long the search goes on" and even what investigators actually do to a computer during their search.

Worries around each of these areas are legitimate, said McAndrew, now a partner at Ballard Spahr LLP, but believes the warrant updates are needed.

"I spent over two years investigating cybercrime on the dark web pretty exclusively, and hiding through technological means was part of every one of those cases," he said, citing experience chasing child pornographers.

"This is the new daily reality, or the current daily reality, for investigators," McAndrew added. "And it's about time, quite frankly, that this rule has been updated from where it began in 1917 to where we are now in terms of trying to combat what are really anonymous mass criminal schemes."