This is normal. The fix often uses the AppID for "SpaceWar" (a developer tool) to route multiplayer data through Steam.
Real-time protection often flags Steamworks fixes as "false positives." Temporarily disable your antivirus or add your Arma 3 folder to the exclusions list. arma 3 mp cracked steamworks fix nino23 link
You must have a Steam account logged in and running in the background. Many users prefer using a "throwaway" or "dummy" account for safety. This is normal
Search for servers that have BattlEye disabled or are labeled as "Cracked" or "No-CD." arma 3 mp cracked steamworks fix nino23 link