Best practices for configuring Windows Defender Firewall

Applies to

Windows operating systems including WindowsВ 10

Windows Server Operating Systems

Windows Defender Firewall with Advanced Security provides host-based, two-way network traffic filtering and blocks unauthorized network traffic flowing into or out of the local device. Configuring your Windows Firewall based on the following best practices can help you optimize protection for devices in your network. These recommendations cover a wide range of deployments including home networks and enterprise desktop/server systems.

To open Windows Firewall, go to theВ StartВ menu, selectВ Run, typeВ WF.msc, and then selectВ OK. See also Open Windows Firewall.

Keep default settings

When you open the Windows Defender Firewall for the first time, you can see the default settings applicable to the local computer. The Overview panel displays security settings for each type of network to which the device can connect.

Figure 1: Windows Defender Firewall

Domain profile: Used for networks where there is a system of account authentication against a domain controller (DC), such as an Azure Active Directory DC

Private profile: Designed for and best used in private networks such as a home network

Public profile: Designed with higher security in mind for public networks like Wi-Fi hotspots, coffee shops, airports, hotels, or stores

View detailed settings for each profile by right-clicking the top-level Windows Defender Firewall with Advanced Security node in the left pane and then selecting Properties.

Maintain the default settings in Windows Defender Firewall whenever possible. These settings have been designed to secure your device for use in most network scenarios. One key example is the default Block behavior for Inbound connections.

Figure 2: Default inbound/outbound settings

To maintain maximum security, do not change the default Block setting for inbound connections.

Understand rule precedence for inbound rules

In many cases, a next step for administrators will be to customize these profiles using rules (sometimes called filters) so that they can work with user apps or other types of software. For example, an administrator or user may choose to add a rule to accommodate a program, open a port or protocol, or allow a predefined type of traffic.

This can be accomplished by right-clicking either Inbound Rules or Outbound Rules, and selecting New Rule. The interface for adding a new rule looks like this:

Figure 3: Rule Creation Wizard

This article does not cover step-by-step rule configuration. See the Windows Firewall with Advanced Security Deployment Guide for general guidance on policy creation.

In many cases, allowing specific types of inbound traffic will be required for applications to function in the network. Administrators should keep the following rule precedence behaviors in mind when allowing these inbound exceptions.

Explicitly defined allow rules will take precedence over the default block setting.

Explicit block rules will take precedence over any conflicting allow rules.

More specific rules will take precedence over less specific rules, except in the case of explicit block rules as mentioned in 2. (For example, if the parameters of rule 1 includes an IP address range, while the parameters of rule 2 include a single IP host address, rule 2 will take precedence.)

Because of 1 and 2, it is important that, when designing a set of policies, you make sure that there are no other explicit block rules in place that could inadvertently overlap, thus preventing the traffic flow you wish to allow.

A general security best practice when creating inbound rules is to be as specific as possible. However, when new rules must be made that use ports or IP addresses, consider using consecutive ranges or subnets instead of individual addresses or ports where possible. This avoids creation of multiple filters under the hood, reduces complexity, and helps to avoid performance degradation.

Windows Defender Firewall does not support traditional weighted, administrator-assigned rule ordering. An effective policy set with expected behaviors can be created by keeping in mind the few, consistent, and logical rule behaviors described above.

Create rules for new applications before first launch

Inbound allow rules

When first installed, networked applications and services issue a listen call specifying the protocol/port information required for them to function properly. As there is a default block action in Windows Defender Firewall, it is necessary to create inbound exception rules to allow this traffic. It is common for the app or the app installer itself to add this firewall rule. Otherwise, the user (or firewall admin on behalf of the user) needs to manually create a rule.

If there are no active application or administrator-defined allow rule(s), a dialog box will prompt the user to either allow or block an application’s packets the first time the app is launched or tries to communicate in the network.

If the user has admin permissions, they will be prompted. If they respond No or cancel the prompt, block rules will be created. Two rules are typically created, one each for TCP and UDP traffic.

If the user is not a local admin, they will not be prompted. In most cases, block rules will be created.

In either of the scenarios above, once these rules are added they must be deleted in order to generate the prompt again. If not, the traffic will continue to be blocked.

The firewall’s default settings are designed for security. Allowing all inbound connections by default introduces the network to various threats. Therefore, creating exceptions for inbound connections from third-party software should be determined by trusted app developers, the user, or the admin on behalf of the user.

Known issues with automatic rule creation

When designing a set of firewall policies for your network, it is a best practice to configure allow rules for any networked applications deployed on the host. Having these rules in place before the user first launches the application will help ensure a seamless experience.

The absence of these staged rules does not necessarily mean that in the end an application will be unable to communicate on the network. However, the behaviors involved in the automatic creation of application rules at runtime requires user interaction.

To determine why some applications are blocked from communicating in the network, check for the following:

A user with sufficient privileges receives a query notification advising them that the application needs to make a change to the firewall policy. Not fully understanding the prompt, the user cancels or dismisses the prompt.

A user lacks sufficient privileges and is therefore not prompted to allow the application to make the appropriate policy changes.

Local Policy Merge is disabled, preventing the application or network service from creating local rules.

Figure 4: Dialog box to allow access

Establish local policy merge and application rules

Firewall rules can be deployed:

1. Locally using the Firewall snap-in (WF.msc)
2. Locally using PowerShell
3. Remotely using Group Policy if the device is a member of an Active Directory Name, System Center Configuration Manager (SCCM), or Intune (using workplace join)

Rule merging settings control how rules from different policy sources can be combined. Administrators can configure different merge behaviors for Domain, Private, and Public profiles.

The rule merging settings either allow or prevent local admins from creating their own firewall rules in addition to those obtained from Group Policy.

Figure 5: Rule merging setting

In the firewall configuration service provider, the equivalent setting is AllowLocalPolicyMerge. This setting can be found under each respective profile node, DomainProfile, PrivateProfile, and PublicProfile.

If merging of local policies is disabled, centralized deployment of rules is required for any app that needs inbound connectivity.

Admins may disable LocalPolicyMerge in high security environments to maintain tighter control over endpoints. This can impact some apps and services that automatically generate a local firewall policy upon installation as discussed above. For these types of apps and services to work, admins should push rules centrally via group policy (GP), Mobile Device Management (MDM), or both (for hybrid or co-management environments).

Firewall CSP and Policy CSP also have settings that can affect rule merging.

As a best practice, it is important to list and log such apps, including the network ports used for communications. Typically, you can find what ports must be open for a given service on the app’s website. For more complex or customer application deployments, a more thorough analysis may be needed using network packet capture tools.

In general, to maintain maximum security, admins should only push firewall exceptions for apps and services determined to serve legitimate purposes.

The use of wildcard patterns, such as C:*\teams.exe is not supported in application rules. We currently only support rules created using the full path to the application(s).

Know how to use «shields up» mode for active attacks

An important firewall feature you can use to mitigate damage during an active attack is the «shields up» mode. It is an informal term referring to an easy method a firewall administrator can use to temporarily increase security in the face of an active attack.

Shields up can be achieved by checking Block all incoming connections, including those in the list of allowed apps setting found in either the Windows Settings app or the legacy file firewall.cpl.

Figure 6: Windows settings App/Windows Security/Firewall Protection/Network Type

Figure 7: Legacy firewall.cpl

By default, the Windows Defender Firewall will block everything unless there is an exception rule created. This setting overrides the exceptions.

For example, the Remote Desktop feature automatically creates firewall rules when enabled. However, if there is an active exploit using multiple ports and services on a host, you can, instead of disabling individual rules, use the shields up mode to block all inbound connections, overriding previous exceptions, including the rules for Remote Desktop. The Remote Desktop rules remain intact but remote access will not work as long as shields up is activated.

Once the emergency is over, uncheck the setting to restore regular network traffic.

Create outbound rules

What follows are a few general guidelines for configuring outbound rules.

The default configuration of Blocked for Outbound rules can be considered for certain highly secure environments. However, the Inbound rule configuration should never be changed in a way that Allows traffic by default.

It is recommended to Allow Outbound by default for most deployments for the sake of simplification around app deployments, unless the enterprise prefers tight security controls over ease-of-use.

In high security environments, an inventory of all enterprise-spanning apps must be taken and logged by the administrator or administrators. Records must include whether an app used requires network connectivity. Administrators will need to create new rules specific to each app that needs network connectivity and push those rules centrally, via group policy (GP), Mobile Device Management (MDM), or both (for hybrid or co-management environments).

For tasks related to creating outbound rules, see Checklist: Creating Outbound Firewall Rules.

Document your changes

When creating an inbound or outbound rule, you should specify details about the app itself, the port range used, and important notes like creation date. Rules must be well-documented for ease of review both by you and other admins. We highly encourage taking the time to make the work of reviewing your firewall rules at a later date easier. AndВ neverВ create unnecessary holes in your firewall.

Can You Rely on Windows Defender in 2021?

Windows Defender comes for free with the latest operational system Windows 10. According to statistics, most modern-day users think that they’ll be perfectly safe with this free antivirus. But is it really that good, is it capable of protecting your device from every single online threat? Compared to the previous antivirus solutions from Microsoft, the Windows Defender is a serious step in the right direction.

It automatically installs with the system and guards it 24/7, until the user downloads third-party software. This antivirus might lack some key features that other products have, but it is more than good enough. Plus, this is one of the quietest anti-malware programs on the market as it doesn’t bother the users with millions of pop-up menus.

However, compared to third-party products, it is slightly dragging behind, which is continuously being proved by lab test results. Even the free editions of industry-leading products like Avast, Bitdefender, and Kaspersky perform better. Let us go ahead and talk more about these lab tests and see how the Windows Defender holds up against the best offers on the market (or just check one of the best antivirus software for 2021).

Is Windows Defender Good Enough in 2021?

The pros of the Win Defender include low system impact, constant free updates, full support by Microsoft, and decent protection. To get the complete picture and to see exactly how bad or good this antivirus is, we need to compare it to other free solutions.

AV-Test is one of the most respected third-party testers – they’ve been in the business for 15+ years. They rank each product based on three factors (the worst score is zero, while the best is six).

The three factors include Performance, Protection, and Usability. In February 2021, tests showed a substantial improvement over the April 2018 results. Win Defender received 6 points in protection and 5.5 in both Performance and Usability. In real-time tests against malware attacks, it managed to earn a 99.6% score.

AV-Comparatives has a slightly different approach, and it helps to understand an antivirus’s performance better. With a zero percent compromise rate, a 99.1% blocking rate, and 106 positives, Windows Defender looks more than decent.

In March 2015, it could only block 80.5% of malware attacks, while the Protection rating was as low as 3.5/6. Back then, the average result was 97.2% in the industry – yes, Defender was well behind the leaders.

It is clear that Microsoft has been working hard to perfect the original formula. Today, their one of the best free antivirus solution is very well capable of protecting users from a vast majority of online threats. Next, let us take a look at how the best free third-party products perform in the same tests to come up with a verdict for Defender.

What Windows Defender Competitors Have to Offer?

As you can see, Win Defender performs quite well in the world’s most trusted tests. Still, it is not exactly on par with the best products. If we take a look at AV-Test Best antiviruses chart, we won’t find Windows Defender among the Top Products. As we have already mentioned, AV-Test evaluates antivirus solutions with regard to protection, performance, and usability. All the Top Products can boast a total score of 17.5 to perfect 18, while Windows Defender got 17 points.

Should you consider getting one of the antiviruses with the top score? Products like McAfee or F-secure definitely offer better protection, more features, and simpler interface. And they will cost you money.

The only free top product in AV-Test chart is Avast. So, is it any better than Windows Defender? From the chart itself, it’s clear you’ll get better usability, and that’s it. If you dig dipper and read Avast antivirus review, you’ll find that extra features Avast offers include a free password manager and free web browser. Moreover, another lab, AV-Comparatives awarded Product of the Year 2018 title to Avast.

At the same time, according to the latest real-world protection test, Win Defender offers industry-leading compromise rate. It is on par with Bitdefender and F-Secure, while Avast shows less perfect results.

Need more information?

The Verdict

Summing up, while Windows Defender is a decent antivirus, it’s not the best free solution. According to AV-Comparatives and AV-Test, it is getting very close to becoming an excellent free product, but it is not there yet. As the tests prove, Avast, McAfee, Bitdefender and Bullguard are some of the best options for you.

A couple of years ago, the thought alone of using the Win Defender as the only antivirus would be strange. In 2021, it is a competent solution, a viable pick for regular users. We still highly recommend installing one of the top-score products we mentioned in this article to be 100% sure you’ll well-protected. As for Microsoft’s free antivirus, we hope that in the nearest future, it will become one of the leaders.

The most significant advantage of this product over Security Essentials, the previous anti-malware software, is that you don’t have to find a third-party alternative immediately. Of course, the tests we discussed earlier did show that it’s not in the top-10. But, it performs significantly better than ever before and won’t let new malware infect your system.

User Reviews

“We still highly recommend installing one of the top-score products we mentioned in this article to be 100% sure you’ll well-protected.”

Sorry but there is no way an antivirus can 100% protect your PC, that’s completely impossible.
Whether you use Kaspersky, BitDefender, Avast and other AV’s you aren’t guaranteed 100% protection.

No consideration has been given, in your article, to the fact that Avast, for just one example, has been caught recently, red-handed, stealing user web browsing data and selling it to the highest bidder. Any time you buy a third party antivirus product, you are trusting that third party, many of whom are quite willing to abuse your trust. Microsoft is not perfect but it has too much to lose not to disclose, for example, its use of telemetry in Windows 10, and you can use products like ShutUp10 to turn it off. Also, the built in antivirus is already there, whereas adding Avast, Norton, Kaspersky, etc. takes up about 1 gigabyte of space on your disk, and slows down the Windows operating system. I’ll continue to use Microsoft Windows Defender.

Funny you updated the article in December but have score from february. Windows defender has 17.5 score now. Guess it top class now?

Hello, Dan,
Thanks for pointing out, indeed 17 is a good score for a free in-build product. And yes, December 2019 comes after February 2019. The article will be updated shortly, stay tuned.