‘Very difficult to defend’: What happens if hackers are inside the Pentagon’s networks? December 27, 2020 The U.S. Department of Defense faces a tough challenge assessing its networks after suspected Russian hackers may have had access for months. (Aislan13/Getty Images) WASHINGTON — If Russian hackers suspected of a vast cybersecurity breach slipped into the Pentagon or military’s computer systems, the strength of protective network blockades is key to keeping them from burrowing in to try to access increasing amounts of information. Those protections — in the form of secure network connections — have to stand up to meddling to keep hackers from hopping from network to network to potentially reach sensitive communications or even weapon systems, where they could steal or alter data or cause damage, experts say. However, observers point out that this breach appears so far to be a classic espionage campaign, though with some of the most sophisticated methods seen yet.