The MsMpEng.exe Antimalware Service Executable process is an antivirus application provided by Microsoft. The Microsoft Defender Antivirus program guards the Windows operating system against malware and any kind of infection. This process scans all files upon opening or downloading them and conducts either scheduled or manual scanning for any infections. It is completely safe to see the process running in Task Manager; however, at some times you might experience increased utilization of CPU, memory, or disk resources when scanning is conducted. When the process regularly slows down your computer, make sure to update the Defender program and wait until scans are done.