A Large Number of Conflicting Firewall Rules: If an old installation of a 3 rd party firewall has included thousands of inbound/outbound rules, while Windows defender has its own such rules, these conflicting rules may require the firewall to use the excessive CPU to execute all of them.Conflicting Firewalls: If you are using another firewall (especially, that is using the Windows Defender API) along with the Windows firewall, the two may conflict with each other, resulting in high CPU usage.Many things can trigger a high CPU usage by the LocalserviceNoNetworkFirewall but we identified the following chiefly responsible for the issue: LocalserviceNoNetworkFirewall High CPU Usage Usually, this service does not use much CPU or memory.īut the issue arises, when this service starts eating a chunk of memory along with high CPU usage (in some cases, more than 50%) and causes the system to be so sluggish that it becomes impossible to use the system. LocalserviceNoNetworkFirewall is a part of Windows security and is used by Windows Defender (or by other Windows API-based firewalls) in their operations.

Windows firewall manager