Same issue. I was just in the Tower. Avast detected it. Game auto closed and the avast warning alarm went off. After looking through my virus chest I realized that the same issue has happened before (months ago) but the file was flagged "IDP.Generic" instead of "IDP.SEMS.BIFROST2". Avast was also telling me I needed to restart, possibly to update? Not sure if directly related to the event. Steam automatically redownloaded the Destiny EXE on restart. I ran the file through Virus Total with no detections. Ran the whole Destiny 2 folder through Avast again and no detections. Running the game and waiting to see if it happens again. If it does, I will be concerned that the integrity of Destiny has somehow been breached... would feel safer with clarification from Bungie either way.