Antimalware Service Executable - Windows Defender Service - Large Network Usage

Antimalware Service / Windows Defender Service is using a large amount of network resources quite often on my machine. I am trying to first pinpoint WHY this is happening, before I move forward with a few ways to curb it from happening.

Screenshot:

My hunch is that I have Crashplan running on my PC, which is looking at a network drive and locally transfering data from NAS to Desktop PC, where it sends to the Crashplan cloud for backup - and Windows Defender sees it as new data so it's trying to scan it every time.

In any case, I also don't want to stop Windows Defender from scanning what it should in real time, I just don't want it to do it if it's from an internal network resource headed to crashplan (if this is the culprit) which has undoubtedly already been scanned.

So to be clear, I am looking for ways to pinpoint why it does this and then stop it from happening IF that is desired. I want Defender to do what it does to help protect the PC, but not at the cost of high resource usage even on my internal network only.

My reference for possibly disabling if desired in the future: Disabling Microsoft Antimalware service

Solution 1:

You could try to add folder exclusion or a process exclusion, for more infomation click here,
or try to use a differnt antivirus

Solution 2:

I know this is kind major necro response, but if you by chance never got this figured out, I was having the same issue and just for curiosity sake I tested something.

I run a Plex server off my PC with all my A/V stuff stored on my dual Drive NAS. This is also a clean install of Windows. I just happened to be in task manager and noticed that it was using around 400-700Mbps constantly and also eating up cpu cycles running my cpu in to the upper 60C range.

Anyways, I had went ahead and excluded my NAS drives as suggested above but it made no change. I looked in procmon as another here suggested but I could find what it was trying to look at. Anyway, I decided to close out Plex Media Server and voila, no more Network usage and my temps and cpu usage dropped instantly.

I added the app to the exclusion and it seemed to work, at least for about 5 minutes, then I saw my temps on the rise, checked Task Manager and sure enough, back up to around 400-700Mbps again. I closed Plex Media Server and again, no usage. I'll check in the morning to see, but it seems Defender dislikes Plex.