I've had this problem for at least several months. I noticed a lot of threads without a happy ending:

1. High CPU Usage from "Service Host: Local Service [...]

2. Service Host: Local Service (No Network) (3) and Service Host: Internet Connection Sharing (ICS) causing High CPU

3. svchost.exe Service Host: Local Service (No Network) - Permanent CPU usage

4. service host: Local Service (No Network) (5) taking up all my CPU resources (i5-4690k)

And I did try all the suggestions made in these threads including:

1. Updating the windows to the latest version
2. Troubleshoot network, update, etc
3. killing all other software, changing MSISUPPORTED of my SSD disk in regedit etc.

One thing I noticed is that the problem disappears in safemode.

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1 Answer

I solved my problem by restoring Windows Defender Firewall to default settings, as mentioned in this post. A very nice explanation and debugging is also given in this superuser reply.

I think some problematic software had access to network. After this reset, windows pops up "Windows Security Alert" again, asking for network privileges, on opening most software for the first time.

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