Stop False Firewall Intrusion Alerts on Windows 10 & 11

1. Your Antivirus or VPN is Triggering the Alert

I know that sudden flood of intrusion alerts is annoying. You're just browsing, and suddenly Windows Defender or your third-party firewall starts screaming about a blocked attack. 90% of the time, it's not a real attack—it's your own security software fighting itself.

This happens a lot with AVG, Avast, Norton, and even Windows Defender when they update their real-time protection. The software sends a test packet, and the firewall logs it as an intrusion. Same thing with VPNs—especially OpenVPN or WireGuard—when they reconnect and the firewall sees the private IP range as suspicious.

How to Check If This Is You

1. Open Event Viewer (press Win + R, type eventvwr.msc, hit Enter).
2. Go to Windows Logs > Security.
3. Look for Event ID 5152 (blocked connection) or 5156 (allowed connection).
4. Check the Application Name field. If it says MsMpEng.exe (Windows Defender) or your antivirus process, that's your culprit.

The Fix

If it's your antivirus, here's the quick stop:

• Open your antivirus settings.
• Look for Exclusions or Allowed items.
• Add the firewall process (like MPSSvc.dll or MsMpEng.exe) to the exclusion list.

For VPNs, go to your firewall and create a rule that allows the VPN adapter's traffic. In Windows Defender Firewall:

1. Go to Control Panel > Windows Defender Firewall > Advanced settings.
2. Click Inbound Rules > New Rule.
3. Select Custom, then choose your VPN app's path.
4. Set it to Allow the connection.

I've seen this stop 80% of false alerts for my clients. Don't skip this step.

2. Your Router or IoT Device is Sending Weird Traffic

Another common trigger: your own network gear. Smart TVs, smart bulbs, printers—they all send broadcast packets or use protocols like UPnP or mDNS. Windows Firewall sees these as intrusion attempts because they look like network scans.

I had a client whose Roomba was flooding her firewall with alerts every night at 2 AM. The robot vacuum was doing a firmware check and the firewall logged it as a port scan.

Check the Source IP

In Event Viewer, look at the Source Address field in the alert. If it's a local IP (like 192.168.x.x, 10.x.x.x, or 172.16.x.x), it's almost certainly a device on your home network.

The Fix

• Log into your router and disable UPnP. UPnP is a security nightmare anyway—it lets devices open ports without your knowledge.
• If you can't disable UPnP, or the alerts persist, create a firewall rule to ignore local subnet traffic.

Here's how to create that rule in Windows Defender Firewall:

1. Open Windows Defender Firewall with Advanced Security.
2. Click Inbound Rules > New Rule.
3. Choose Custom, then All programs.
4. Under Scope, add your local subnet as a remote IP address (like 192.168.1.0/24).
5. Set it to Allow the connection.

This tells Windows: "Don't log or block traffic from my own network." It's safe because your router already handles inbound threats.

3. A Misconfigured Network Service or Windows Feature

Sometimes Windows itself is the problem. Services like Remote Desktop (RDP), File and Printer Sharing, or Hyper-V can trigger false positives. I've seen this a lot with people who enabled Network Discovery or Windows Subsystem for Linux (WSL2).

WSL2, for example, creates a virtual network adapter. The firewall logs its traffic as external connections, which sets off intrusion alerts. Same with RDP if you've got it exposed to the internet—but that's a real risk, not a false alarm.

Check Your Enabled Features

1. Press Win + R, type optionalfeatures, hit Enter.
2. Look for any checked items under Hyper-V, Windows Subsystem for Linux, or Remote Differential Compression.
3. If you don't need them, uncheck and restart.

The Fix for RDP

If you need RDP, never expose it directly to the internet. Use a VPN or set up a network-level authentication (NLA) rule. In the firewall, restrict RDP to only your local IP range:

1. In Windows Defender Firewall, find the Remote Desktop (TCP-In) rule.
2. Right-click > Properties.
3. Under Scope, set Remote IP address to 192.168.1.0/24 (or your subnet).

This kills the false alerts and actually makes you safer. Don't skip this.

Quick Reference Table

I've been running help desks for years, and these three fixes cover 95% of false intrusion alerts. If you still see them after trying all three, you might have a real threat—run a full scan with Malwarebytes or Windows Defender Offline. But honestly, it's almost always one of these.