LocalServiceNoNetworkFirewall Consumes Large Amount of CPU on a Regular Basis

This same thing has happened to me. One thing you can try is to reset your Windows Firewall to default settings:  https://theitbros.com/reset-windows-10-firewall-settings-default/

However this has not helped me and I am still in this position after hours of troubleshooting. I hope that a Microsoft rep will respond with some tips.

I have tried the following on my Lenovo AMD laptop which is running Windows 10 1909:

• Check Lenovo updates - all up to date
• Check Windows updates - all up to date
• System file check - no issues
• DISM /Online /Cleanup-Image /CheckHealth - no problems
• DISM /Online /Cleanup-Image /RestoreHealth - no problems
• Checked Reliability History - nothing obvious highlighted related to this CPU issue
• Check for updates to LAN/WLAN driver - latest already installed
• Ran the Lenovo diagnostic tool on relevant hardware. No hardware faults found, including memory, network, CPU devices
• I have installed an optional Windows update KB4550945 (April 2020)
• Power cycled machine
• Reset firewall to default in Windows 10 settings menu

The issue is casing the laptop to be very sluggish and difficult to use. The laptop itself is only a few weeks old.

Please try disabling IP Layer Enforcement for Cisco Umbrella. This feature can trigger the local firewall to use CPU, but the expected design should only consume higher CPU for approximately 60 seconds while setting up the IP blocks. There's a possible issue we're seeing with this feature, where the system is also utilizing Hyper-V. We have a fix planned but it is not released yet. Note: I work for Cisco

We were facing this issue too, so we opened case at Microsoft support and the engineer found erc_service.exe as root cause too.

We opened case at CISCO support and the recommendation was to disable IP Layer enforcement, so I confirm what adamwinn said.

I have the same issue with three CPU's that do not have a Cisco product installed. Both have AVG and HP Support Assistant installed. With one was installing HP's Recovery Assistant software in order to make a recovery disc. The attempt was unsuccessful multiple times. I also tried to complete a recovery disc using MS' system tool and was unsuccessful. What I have noticed with all three is corrupted files in the System32 directory which a recovery install does not correct. This is an operating system issue caused during a recent upgrade. Unfortunately, I do not know which one is the culprit.

I had this same problem this past April-June 2020, and posted comment on it in June here:

https://answers.microsoft.com/en-us/windows/forum/all/localservicenonetworkfirewall-does-microsoft-ever/97878d20-441b-4ea0-87bb-004ef399f9d5

This time LocalServiceNoNetworkFirewall not only seems to fire up when trying to open a PDF file, but seems to block my ability to open any new app window for minutes at a time.

Until about a week ago, the problem went away soon after my June post, and I was happy that it somehow went away, but now it is more frustrating than ever.

I see you mention AVG, which is something I wondered about as well, since AVG is also doing firewalling, so I wonder if Windows Defender and AVG are somehow conflicting?

Do others that are seeing this problem run AVG?

Frustrating that Microsoft has offered no solution to this. 

My laptop is nearly unusable at this point. Takes 6-9 restarts to get the Avast! Firewall to turn on; each failed launch corresponds to the localservicenonetworkfirewall, and i cannot force start the firewall in task manager services. Even the cursor struggles to move when I move the mouse!

Windows Firewall is disabled, and I am not even connected the internet on startup, and Windows Security claims there are no providers for firewalls. (maybe this is the MS way to punish me for choosing something over the native software...)

Frustrating that Microsoft has offered no solution to this. 

My laptop is nearly unusable at this point. Takes 6-9 restarts to get the Avast! Firewall to turn on; each failed launch corresponds to the localservicenonetworkfirewall, and i cannot force start the firewall in task manager services. Even the cursor struggles to move when I move the mouse!

Windows Firewall is disabled, and I am not even connected the internet on startup, and Windows Security claims there are no providers for firewalls. (maybe this is the MS way to punish me for choosing something over the native software...)

Hi There. I have the same problem. Any fix out there yet?