Recently I scanned my computer and the antivirus shown that there are several files (msmpeng.exe) are infected (and one of them is infected by trojan) but I can't do anything to deal with them...Please help!
You have windows defender installed ?
- it is loading unencrypted virus signatures into memory.
You are running a custom scan - you have elected to scan Memory ?
These detections are in memory and are loaded by msmpeng.exe it doesn't mean that msmpeng.exe is infected.
- Detections in Memory - The Custom scan in which you have elected to scan Memory and that all these detections are in memory or are listings of files that can't be scanned. Since they aren't physical files they can't be moved to the chest, deleted, etc. so there is no action that can be taken, hence the Apply button being greyed out.
The detections in memory are frequently other security applications loading unencrypted virus signatures into memory.
Having set off a scan of memory by an antivirus application looking for virus signatures, don't be too surprised if it finds some in memory.