The Steam ‘teraleak’ extends far beyond Valve games, including prototypes of third-party titles like Mafia 2 and Grand Theft Auto 3: ‘This may be one of if not the biggest leaks to occur’

On Saturday, information began circulating online about a massive, 12-terabyte leak of Valve data that included prototypes of numerous classic Valve games. But it seems what is now being dubbed the “teraleak” contained far more than just old builds of Portal 2 and possible weapons from Half-Life 2: Episode 3, and may include prototypes of countless third-party games released on Steam over a ten-year period.

Specifically, the leak consists of Steam file groups known as ‘depots’ which were stored on Steam’s servers between 2003 and 2013. A full list of these depots was shared on Reddit by user RefreshingCapybara, which includes depot names for hundreds of games as well as trailers, teasers, soundtracks, demos, game trials, and more. “Not to be hyperbolic, but this may be one of if not the biggest leaks to occur,” RefreshingCapybara commented in sharing the list.

To be clear, the list doesn’t show us what—if anything—is contained within those file groups. But as reported by Ars Technica, game preservation website Hidden Palace has identified numerous depots with obtainable builds in them. These include various prototypes of Spec Ops: The Line, Sid Meier’s Civilization V, Mafia 2, and Grand Theft Auto 3.

According to Ars, it’s also likely that the builds included in the leak are from a collection that has been amassed from various sources over time. Many game builds from before 2013—which is when Valve switched its content distribution pipeline from Steam2 to SteamPipe—were considered lost media up to now. Clearly, though, they were more accessible than Valve or anyone else realised.

As such, it’s possible the leak is the product of multiple people pulling together builds from various sources (like old PCs) into one enormous archive. The most interesting clue to the leak’s origins is a readme file contained within the leak, which includes the line “warm n good wishes to all hoarders who had stuff from this collection”.

The fact that the build includes so many third-party prototypes may also make it legally perilous. “That archive contains a significant amount of third-party content, meaning we are dealing with a dramatically more dangerous situation than if it were just some Valve builds,” wrote YouTuber and Valve specialist Tyler McVicker on social media.

Given the sheer amount of data that has been leaked, it will likely be some time before we know the true extent of what it contains. On the Valve side, dataminers have already unearthed a complete version of Portal 2’s 2009 “beta”, as well as prototypes for Left 4 Dead, Counter-Strike: Global Offensive, and even some files from Valve’s cancelled puzzler F-STOP.