WARNING: The following contains spoilers for Checkmate #3, on sale now from DC.
Three of the most iconic locations in the DC Universe are also three of its most secure. They are the Fortress of Solitude, the Batcave and the Justice League's Hall of Justice. Each has its own unique system, built upon its own unique technology. For Superman, the Fortress is built upon Kryptonian technology and for Batman, the Batcave is run by the best tech that money can buy and that Wayne Enterprises can make. As for the Hall of Justice, its system is a collaborative effort, from some of the greatest minds of the superhero community. However, as Lois Lane just revealed, the League's system is a lot more collaborative than most people, even members of the Justice League itself, realize.
In Checkmate #3 by Brian Michael Bendis, Alex Maleev, Dave Stewart and Josh Reed, Leviathan Mark Shaw makes a bold move towards his new world order by kidnapping Lois Lane. This move proves to be a big mistake as it allows the intrepid reporter to figure out what Leviathan is planning. When she makes her way back to her Checkmate allies she reveals a secret about some of the most secure places in the DC Universe that not even heroes like Green Arrow know.
As Lois reveals, the Batcave, the Fortress and the Hall of Justice are all linked by a super-secret system and all of them share a singular database. This system, nicknamed the Heroes' System, is made up of Superman and Batman's technology, as well as other types of tech from the League's founding members. This is quite the revelation as, before now, it was assumed these locations all had their own unique systems. Though Batman has been able to access the League's files on the Batcomputer before, no one ever suspected that the connection the Batcave and the Hall of Justice shared was ever this deep. Nor did anyone expect Superman's Fortress to be involved.
It's so secret that even Green Arrow, the current leader of the Justice League and the person currently bankrolling the Hall of Justice, didn't know about this secret connection. This seems surprising, especially considering how long Green Arrow has been a part of the League but the threat posed by Leviathan shows why such secrecy is often needed. The more people that know about the Heroes' System, the more of a target it would be. Keeping it as such a closely guarded secret means that situations like the one Checkmate are in now are less likely to happen.
When Leviathan released Lois after kidnapping her, they teleported her, oddly, to the Hall of Justice rather than back to where they found her. This odd occurrence made her realize that the malevolent organization wanted her at the Hall of Justice because they know about the heroes' secret system. Leviathan currently has control of almost all of the world's secrets and technology. This system is the one thing they don't have. If they somehow get a hold of it, then nothing can stop the combined might of Leviathan.
That's why Lois Lane is only telling her fellow Checkmate members about this now. Though they still don't entirely trust one another, the stakes are too high to keep the Heroes' System a secret. Not when it's Leviathan's target and not when losing it could doom the world. Still, it makes sense why even members of the Justice League can't know this information. Mark Shaw, Leviathan's leader, was once a hero and now he's using his knowledge of the heroes to build a frightening new world order. If another hero with access to the League's tech ever turns bad, then the less they know about the secret Heroes' System the better.