The official Dark Souls Twitter account has revealed that servers for Dark Souls 3, Dark Souls 2, and Dark Souls: Remastered have been temporarily deactivated to allow the team to investigate recent reports of an issue with online services.
This stems for a report by Dexerto noting that a vulnerability was found for PC users. This exploit could let hackers take control over ones computer as shown in a recent Twitch stream by The_Grim_Sleeper where the game crashed and received criticism from Microsoft’s text-to-speech program shortly thereafter.
At the time of publishing, FromSoftware and Bandai Namco know of the issue and are still working on a fix. In theory, this should not take long as community-made anti-cheat mod Blue Sentinel has already been updated to protect against this.