Security or Firewall might be blocking the connection

If you cannot connect to the internet or network on your Windows 11 or Windows 10 PC, you may see the message Security or firewall might be blocking the connection when you complete a Windows Network Diagnostics on your device. This post provides the most suitable solutions you can apply to resolve this issue.

Security or Firewall might be blocking the connection

If you see the message Security or firewall might be blocking the connection following completion of Windows Network Diagnostics to determine what’s causing internet or network connection issues on your device, then our solutions presented below in no particular order should help you resolve the issue on your system.

Run Windows Firewall Troubleshooter
Restore or Reset the Windows Firewall to default settings
Temporarily disable third-party security software (if applicable)
Run Network Troubleshooter
Update Killer Network Manager driver (if applicable)
Perform System Restore

Let’s look at the description of the process as it relates to each of the listed solutions.

1] Run Windows Firewall Troubleshooter

To begin troubleshooting the Security or Firewall might be blocking the connection issue on your Windows 11/10 computer, you can run the Windows Firewall Troubleshooter and see if that helps. The Windows Firewall Troubleshooter is a diagcab file and the official Firewall troubleshooter from Microsoft. When you run the troubleshooter, you’ll be taken through step-by-step as the app looks for problems. If a problem is found, it will be explained, and you can choose to repair or exit. To run the troubleshooter, follow these steps:

Download the diagcab file.
Once downloaded, double-click the file to run it or open the wizard.
Follow the steps in the Windows Firewall Troubleshooter.

The automated troubleshooter fixes:

Windows Firewall isn’t the default firewall.
Windows Firewall doesn’t start.
Windows couldn’t start Windows Firewall (Service-specific error 5 (0x5)).
Remote Assistance isn’t working because it’s blocked by Windows Firewall.
You’re unable to access shared files and printers because sharing is blocked by Windows Firewall.
BFE service is missing.
Firewall won’t start (Error Code 80070424).

If you’re not on the computer that has the problem, save the troubleshooter to a flash drive, and then run it on the computer that has the problem.

Read: Windows firewall can’t change some of your settings Error code 0x8007042c

2] Restore or Reset the Windows Firewall to default settings

If your Windows 11/10 computer is blocking connections as it is in this case, the Windows Firewall may be preventing the connections from getting through. The first thing you should do if you suspect a firewall problem is to restart your computer and your network/internet device (including your DSL or cable modem). If the issue persists, you can test to see if the problem is the Windows Firewall by temporarily turning off the Windows Firewall to see if it’s causing the problem. After you test the connection, turn on the Windows Firewall to make sure your computer is protected.

If this test solved the problem, that means that Windows Firewall is blocking the connections. If so, it may help to restore or reset the Windows Firewall to default settings and then restart your PC and see if that helps. This is only the case if you have added custom firewall rules to allow certain programs that would have normally been blocked, which is rare. If you have added custom rules, you may not want to perform this task. During this process which will remove any erroneous firewall rules that are blocking legitimate connections, Windows will notify you that restoring the default firewall settings may cause some programs to stop working. To reset the Windows Firewall, follow these steps:

Press the Windows key + R to invoke the Run dialog.
In the Run dialog box, type control and hit Enter to open Control Panel.
Click Windows Defender Firewall.

If the Control Panel opens in the Category view, click System and Security then click on Windows Defender Firewall.

In the Windows Defender Firewall settings page that opens, click the Restore defaults link on the left navigation pane.
In the Restore default settings page, click the Restore defaults button.
Click Yes. on the confirmation prompt that appears to continue.
Exit Control Panel when done.

Read: Import, Export, Repair, Restore Default Firewall Policy in Windows

3] Temporarily disable third-party security software (if applicable)

On your Windows 11/10 computer, outgoing/incoming connections can be affected by the presence of a firewall or antivirus software (especially from third-party vendors) on the local computer or network connection. As you can see in this our case, the Windows Network Diagnostics identified the Malwarebytes Web Access Controller (MWAC) Filter which is what Malwarebytes uses for the Web Protection component in Malwarebytes (bad website blocking) that relies on the Windows Filtering Platform (WFP) APIs in modern versions of Microsoft Windows which is the same infrastructure/APIs used for the built-in Windows Firewall in newer versions of the Windows OS. Disabling the Web Protection component in MBAM worked for affected users, although this is more of a workaround than an actual solution.

So, you can disable the third-party security software. To do this, you can check the software settings page or consult the user manual. Generally, to disable your security software, locate its icon in the notification area or system tray on the taskbar, right-click the icon and choose the option to disable the program. However, if you do not have third-party security software or dedicated firewall software running on your computer, you can disable Windows Defender Firewall and see if that solves the problem. If it does, you can install and configure any reputable firewall software if that’s an option for you or see if other solutions presented in this post is more preferable and works for you.

Read: PC won’t connect to the internet, but other devices will

4] Run Network Troubleshooter

As this is a network-related issue, a viable solution is to run the inbuilt Network Troubleshooter and apply any recommended fixes to resolve network & internet connection problems on your Windows 11/10 computer.

Read: Can’t connect to this network error on Windows

5] Update Killer Network Manager driver (if applicable)

The Killer Network Manager, previously known as the Killer Control Centre, is a tool from intel.com that helps prioritize the network bandwidth to applications or processes that require faster internet connections. Essentially, the tool is a network management suite developed by Killer Networking for Killer network adapter users.

Some affected PC users reported they were able to resolve the issue by simply updating the Killer Network Manager driver. If this applies to you, you can update the Killer network adapter driver via Device Manager or visit the network adapter manufacturer’s website.

Read: SmartByte Network Service causes slow Internet speed on Windows

6] Perform System Restore

If the issue in the highlight persists after you have exhausted all other suggestions provided in this post, you can follow the steps below to restore your system to an earlier point in time when you weren’t having any sort of network or internet issues on your Windows 11/10 device.

Press the Windows key + R. to invoke the Run dialog.
In the Run dialog box, type rstrui and hit Enter to launch the System Restore Wizard.
At the initial screen of System Restore, click Next.
At the next screen, check the box associated with Show more restore points.
Now, select a restore point before when you noticed the issue on your device.
Click Next to advance to the next menu.
Click Finish and confirm at the final prompt.

At the next system startup, your older computer state will be enforced. The issue at hand should be resolved now. If not, you can reset the PC.

I hope you find this post helpful!

These posts might interest you:

How do I unblock a firewall connection?

Unblock specific network connection settings by clicking on the “Advanced” tab at the top of the firewall settings window. Locate the “Network Connections Settings” section. Unblock the firewall by removing the check from the box located next to the network type. However, if you get this problem with websites, you need to whitelist in the Windows Firewall, click Start, type firewall, and click Firewall & network protection. Click Allow a program or feature through Windows Firewall (or, if you’re using Windows 10, click Allow an app through the firewall).

Read: How to blacklist or block websites in Chrome, Firefox, and Edge browsers

Why is my firewall blocking everything?

The primary reason why your firewall is blocking everything is because you have set things up incorrectly. Although this problem, generally, doesn’t happen with the in-built firewall app of Windows 11/10 PC, it is very common with third-party utilities. That said, it is recommended that you check all the settings and options of your firewall app.

Read: How to allow Pings (ICMP Echo requests) through Windows Firewall.