PlayStation has long been the gaming console of choice among gamers around the world. Now, it may be used as a channel of communication for ISIS. In the wake of Friday night’s terrorist attacks in Paris, Belgian federal home affairs minister Jan Jambon warned about the growing popularity of Sony’s PlayStation 4 among terror networks, which use the gaming device to communicate with each other and spell out attack plans.

“The thing that keeps me awake at night is the guy behind his computer, looking for messages from [the Islamic State] and other hate preachers,” Jambon said last Friday, according to Brussels weekly, the Bulletin. “PlayStation 4 is even more difficult to keep track of than WhatsApp.”

After the nearly simultaneous sieges in Paris, which left at least 129 dead and 352 injured, authorities in nearby Brussels conducted a number of searches for those responsible and discovered evidence that included at least one PS4 console. Jambon said the Islamic State group, which claimed responsibility for Friday’s attacks, employed the popular gaming console to communicate because it’s difficult to monitor, according to Forbes.

There are several ways ISIS and other terrorists could communicate through the gaming console. PS4 users can send messages through the PlayStation Network online gaming service, use voice-chatting or even communicate through a specific game.

Documents leaked by National Security Agency contractor Edward Snowden in 2013 disclosed that the NSA and CIA actually embedded themselves in online games like “World of Warcraft” and “Second Life,” fearing that terrorist or criminal networks could use the virtual worlds to communicate secretly.

PlayStation’s IP-based voice systems are difficult for investigators to monitor compared to traditional forms of communication such as mobile phones and computers. And terrorists could send messages to each other within PlayStation games without speaking or typing a word. A member of the Islamic State group, also known as ISIS or ISIL, could convey an attack plan in Call Of Duty by shooting at a wall and writing a disappearing message in bullets to another player, Forbes reported.

While it remains unclear whether the militants from Friday’s attacks actually used PS4, the popular gaming console has proven to be an effective avenue of covert communication for both the good guys and bad guys.