How to tell if a Windows problem is caused by the antivirus or the firewall

¿How can you tell if a Windows problem is caused by an antivirus or firewall? When something It stops working properly on Windows. (Internet cuts out, a game won't connect, an app won't start, you can't access the local network…), one of the first logical questions is whether the culprit is the antivirus or the firewallIt's not always obvious, because these tools are designed to protect you, but sometimes they generate false positives, misconfigured rules, or conflicts with other programs.

In this article you will see How to detect if the problem comes from the antivirus, the Windows firewall, or a third-party firewallYou'll learn what to check in each case and how to fix it without leaving your system unprotected. You'll see graphical methods, command-line tools, service checks, logs, external tools, and even how to interpret rules and events to get to the root cause of the problem.

Basic concepts: antivirus, firewall and network profiles

Before you start messing around with settings like crazy, it's important to be clear on the following: What exactly does the Windows firewall do, and what does the antivirus do?Because often both are blamed equally and they don't have the same role.

El Windows Firewall (Microsoft Defender Firewall) It filters network traffic entering and leaving the computer, blocking unauthorized connections based on rules. IP addresses, ports, protocols, and program pathsThe antivirus, for its part, focuses on detecting malware, suspicious behavior, and malicious filesalthough many also include their own integrated firewall. To better understand the existing types, consult the antivirus classification.

Windows organizes network protection by network profilesDomain (managed work environments), private (home or trusted network), and public (Wi-Fi in bars, airports, etc.). Each profile has its own firewall configuration, so Something might work at home but fail on public Wi-Fi. simply for using different rules.

Furthermore, it is key to understand the difference between private and public network in WindowsIn a private network, you accept that other devices on the same network can see your computer and connect to it (for example, a NAS or a PC sharing folders), while in a public network it is normal to close incoming connections as much as possible because you don't know anyone who's online.

As a general rule, the more "suspicious" the network (hotels, cafes, open Wi-Fi), the more Your firewall should be restrictive.This means that some software that was working fine at home might suddenly become unresponsive when switching networks.

How to check if the problem is coming from the Windows Firewall

The first step to determine if a failure is caused by the firewall is to verify that the Windows Firewall is actually active and not disabled by a third-party antivirus or by a company policy.

You can see it by opening the app Windows Security (Search for "Windows Security" or "Firewall and Network Protection" in the taskbar search box.) From there you will see the status of each profile (Domain, Private, Public) and whether the Microsoft Defender Firewall It is either enabled or disabled in each one.

Keep in mind that on some computers, especially where a third-party firewall (Bitdefender, Avast, ESET, etc.) has been installed, the Windows interface may display confusing messages: the profiles appear enabled, but a higher layer indicates that "Windows Firewall is disabled" because the active firewall is the antivirus's.

For a more reliable check, you can use tools like PowerShell, WMI or netsh to check the actual state; in addition, it is useful to know how Block suspicious network connections from CMD If you detect suspicious traffic. For example, with netsh advfirewall show allprofiles You can see if the firewall is in "ON" or "OFF" mode for each profile. If they all appear as ON but you see that the Windows firewall is disabled in the graphical interface, it's most likely that A third-party firewall is managing the protection and Windows only displays the vendor's embedded information.

If you suspect a third-party firewall is interfering, also check the Security Center or Activity Center Windows relies on information via WMI. If the WMI repository is corrupted, the firewall status information can be misleading, and it's advisable to... repair the WMI repository.

See which programs and ports the Windows firewall blocks.

A very effective way to check if a problem is coming from the firewall is see exactly what's blockingThis applies to both ports and programs. The Windows Firewall is more complex than it first appears.

On one hand, the firewall works with entry and exit rulesThese rules can allow or deny traffic for a specific executable, port, or IP range. A typical false positive is that a legitimate program gets blocked because some rule considers him suspicious or puts him on a blacklist.

To review the blocked apps, go to Control Panel > System and Security > Windows Defender Firewall and go to "Allow an app or feature through Windows Defender Firewall." There you'll see a list of all the apps that are they allowed or are they banned? in the firewall, with a column for each type of network (private and public).

If an app that's giving you trouble appears unchecked in the profiles you use, or isn't listed at all, that's a good indication that The firewall is responsible for the failureYou can select it to allow it or add it manually if it doesn't appear.

Regarding ports, the Windows firewall allows you to create a blocked traffic logFrom "Windows Defender Firewall with Advanced Security" (Control Panel > Administrative Tools) you can go to Properties, select the profile you want (public, private or domain), and in the logging section check "Log dropped packets" in YeahThe log file (usually pfirewall.log) is saved in %systemroot%\system32\LogFiles\Firewall.

Opening that log will show you in detail. Which ports and addresses is the firewall blocking?If, just as you try to use an app, a line appears indicating that the traffic has been dropped, you know where the problem is coming from.

Check ports from outside: You Get Signal and other clues

To further confirm whether the blocking is coming from the firewall/ports on your network, you can rely on the following: external toolsOne of the simplest is the website You Get Signal, which is used to check if a specific port is open to the Internet.

This page shows you your Public IP It also has a section called "Port Forwarding Tester." Simply enter the port you want to test and click "Check" to see if it's open or closed from outside your network.

In addition, it includes a list of common ports (21 FTP, 22 SSH, 5900 VNC, 25565 for Minecraft servers, etc.) are commonly used. If a game or service asks you to open a port, you can try opening it there to see if your router and firewall are allowing the traffic.

If the test indicates that the port is closed and you thought you had opened it, you will need to check both the router configuration (port forwarding/NAT) such as Windows firewall rules or your antivirus software. Ultimately, if any of those links breaks the connection, the port will appear closed from the outside.

As an extra tip, if after opening a port on the router and allowing it in the Windows firewall, the test still shows as closed, it's quite likely that a third-party firewall or the antivirus itself is filtering that connection.

How firewall rules work and why they sometimes "get ahead of themselves"

The Windows Firewall engine does not apply all rules at once, but rather Use only one rule to decide what to do with each package.If several rules coincide, follow a fairly important order of priority when investigating problems.

The priority is this: first, rules that allow traffic "if it is safe" are applied, and they also have the option enabled. “Block override”; then come the rules of Block; and finally those of AllowThis means that even if you create a rule to allow an app, if there is another, higher-priority blocking rule, will continue to block traffic.

In the "Monitoring" node of "Windows Firewall with Advanced Security", only the following are displayed: active rules at that timeIf you don't see a rule in that list, it may be because it's disabled or simply because the firewall's default behavior for that direction (inbound or outbound) already allows the traffic and there's no need to show explicit allow rules.

By default, several rule groups are enabled (Primary Networks, Remote Assistance, Network Discovery, etc.). When you install new Windows features or programs, more can be added. additional rules which sometimes conflict with what you have configured afterwards.

If you're trying to figure out if an app is being blocked by the firewall, it's a good idea to check the Monitoring section to see which rules are actually being applied, because that's where the problem lies. You can see which specific rule has determined the connection's fate..

Log activity: firewall logs, auditpol, and netstat

If you want to "go into detail" to diagnose a complex fault, you can rely on several Windows tools that allow you to audit network and firewall activity.

On the one hand, in addition to the firewall log we mentioned, you can use auditpol.exe for configure audit policiesWith commands like auditpol.exe /list /category You can see which event categories can be registered, and with auditpol.exe /set /category:"NombreCategoria" /SubCategory:"NombreSubcategoria" You enable registration for that specific part.

These events will be displayed in the Event Viewerand they help you see, for example, policy changes or security events that affect the firewall or IPSec; you can complement them with programs to prevent intrusions if you suspect malicious activity.

You can also generate a snapshot of the network status by running the following command in a command prompt: netstat -ano > netstat.txt y tasklist /svc > tasklist.txtBy crossing both files you see which processes are using which ports Thanks to the PID (process identifier). This is great for finding out which program is listening on a port you want to open or that appears blocked in the log.

If, after reviewing all of this, you see that there is blocked traffic that shouldn't be, it's quite likely that The firewall (or a specific rule) may be the source of the problem. and not so much the classic antivirus.

Services required for the firewall to function properly

Another reason why the firewall seems to fail (or Windows shows strange states) is that some critical service is downFor "Windows Firewall with Advanced Security" to function correctly, services such as the following must be running:

• Base filter motor (BFE)
• Windows Firewall
• Group policy client
• IPsec key creation modules for IKE and AuthIP
• IP Assistant
• IPsec Policy Agent
• Network location recognition
• Network list service

If any of these services are disabled or in error, the firewall may not applying rules correctly, not identifying the current network profile or even allowing you to open the advanced configuration console without errors.

In that scenario, if you see strange connectivity problems or inconsistencies between what the interface says and what's actually happening, it's a good idea to go to service administrator and make sure that all of these are active and set to automatic startup (except in very specific cases in managed environments).

When the culprit is the antivirus or a third-party firewall

Beyond the Windows firewall, many problems stem from antivirus with integrated firewall such as Avast, Bitdefender, ESET, etc. Sometimes, the Windows Action Center/Security Center detects that they are installed but displays messages like "Avast Antivirus is disabled" or "The firewall is disabled," when in reality they are running.

To rule out that the Windows warning is simply a communication failure with the antivirus, first check that the product itself indicates that “This team is protected”that the license is active and that both the app and the virus definitions are up to date.

If the antivirus includes own firewall (like Avast Premium Security or ESET Internet Security), go into its settings and check that the firewall is enabled (usually shown with a green/on switch). If it's set to ON here, but Windows says it's disabled, the problem is usually in the WMI repositorywhich is where Windows gets the status of security solutions.

In the case of ESET, for example, you have tools such as the window of Troubleshooting network access problemsThis tool displays all network connections blocked by the firewall and allows you to create exceptions in a guided way. You can also use the interactive mode ESET's firewall allows you to accept or deny connections as they occur, creating custom rules based on real traffic.

If you have a third-party firewall and the problem temporarily disappears when you disable it, but not when you disable only the Windows Firewall, it's pretty clear that It is that product that is cutting the connectionsIn that case, your job will be to adjust their rules (or consider changing solutions) rather than touching the Microsoft firewall.

Why disabling the firewall is not a good idea (except for specific tests)

Many people, when in doubt, take the easy way out: disable the firewall Let's see if "everything works" this way. This can serve as a one-off test to confirm if the problem originates there, but leaving it permanently turned off is like leave your house with doors and windows open.

Without a firewall, all your computer's ports are exposed as open or accessible, and you are much more likely to fall victim to malware, intrusions, or automated scansThe firewall is precisely what regulates which ports are seen and which are not, as well as which applications can use the network.

The reasonable thing to do, if you suspect the firewall is causing the problem, is Deactivate it for just a few minutes To check if the problem disappears. If everything works after doing this, you have confirmation that the firewall (either Windows or a third-party one) is the culprit, and then you should look for the appropriate rule or exception; don't leave it turned off.

In any case, if you've been loosely bending the rules and starting to see strange behavior, remember that you can always... restore firewalls to default values from the Windows console itself, which returns the configuration to the original system state (although in business environments domain policies will be reapplied).

As a general rule, a firewall should protect, but not become a constant obstacle. If you notice that everything fails except when it's disabled, something in the configuration is clearly out of place and deserves a thorough review.

Risks and benefits of open ports

The network ports They're like numbered ports on your network connection. For many services to work (online games, video calls, NAS servers, P2P applications, etc.), some ports need to be open, but that doesn't mean it's a good idea to have them open. everything open without control.

When you keep unused ports open, you're leaving entry points that others can exploit. malware or attackersMany malicious codes look for specific ports to launch attacks; intrusion alerts The router can alert you to access attempts; a successful intrusion into the router can compromise all devices on the network: DNS modification, Man-in-the-Middle attacks, use of the router in DoS attacks, creation of fake Wi-Fi networks that mimic yours, etc.

However, sometimes it is essential to open ports: for example, to play online with a console or PC game that needs to communicate with remote servers; to improve speed in P2P applications; to allow remote access to a NAS or home server; or to video call programs like Skype, to function smoothly.

The key is in Open only the necessary ports, to the fewest possible destinations, and with additional security measures. (updated signatures, up-to-date systems, strong passwords, etc.). Any unusual symptoms associated with a newly opened port should make you wonder if the firewall is handling it properly or if another app is filtering that traffic.

If you continue to experience disconnections after opening a port for a game, for example, check your firewall, router, and antivirus software. Many of these apps create automatic rules, but others require manual configuration. manually add the exception.

Port forwarding and its relationship with the firewall

El port forwarding Port forwarding is a technique that allows an external user on the internet to access a service located within your LAN, typically behind a router with NAT. This is achieved by redirecting a WAN port on the router to an internal machine and port.

This is usually used to allow someone from outside to access a NAS server, web server, dedicated gaming server, remote desktopetc. The problem is that, even if you forward the traffic on the router, if Windows has the port blocked in your firewallThe traffic will still not reach the application.

In Windows 10/11 you can manage it from "Windows Defender Firewall with advanced security". There you have the Entry rules (for incoming traffic) and the Exit Rules (for what it outputs). Port forwarding usually refers to incoming traffic, so you should create an inbound rule that allows the appropriate port and protocol (TCP or UDP).

When creating a new port rule, you can allow "All local ports" or specify one port or a range. Ideally, Open only the specific port you needSelect whether to use TCP or UDP, and then specify which network profiles it will apply to (domain, private, or public). Finally, give it a descriptive name so you can easily identify it.

If you do this and still don't have a proper connection, check the firewall log to see if packets are being dropped for that port, and verify that there is no other prior rule that is blocking the same traffic with higher priority.

Controlling the Windows firewall with Netsh

When the graphical interface isn't working properly or you need to automate tasks, you can resort to Netsh (Network Shell), a command-line utility included in Windows. From there you can enable or disable the firewall, create rules for specific ports, delete rules, or even restore default values.

Open a command prompt or Terminal as administrator, type netsh advfirewall and you'll see a set of commands available to control the firewall. For example, to activate firewall in the current profile you can use netsh advfirewall set currentprofile state on.

If you want to enable port 80 for incoming traffic from the command line, you could run something like this: netsh advfirewall firewall add rule name="Open Port 80" dir=in action=allow protocol=TCP localport=80This will create an inbound rule that allows TCP traffic on that port.

It is also possible delete rules for programs or ports, or directly reset all settings with netsh advfirewall resetThis is useful if you've made a lot of test changes and the firewall starts behaving in a way that's hard to understand.

If, after completely resetting the settings, your connectivity problem disappears, you can be fairly certain that A previous firewall rule was causing the failure and not so much the antivirus or other system elements.

Online games, antivirus, and connection blocks

A very common case where it is difficult to distinguish culprits is that of play onlineThere are constant disconnections, ping spikes, the game won't connect to the servers or crashes after a short time. Several factors usually contribute to this: firewall, antivirus, router ports, game plugins, VPN, etc.

Often the problem is due to the The antivirus detects the game or some add-on as a false positive.In other words, it identifies the behavior as suspicious even if it's legitimate, and blocks access to the network or the executable itself. It could also be due to an overly aggressive configuration of the built-in firewall.

The first practical test is to deactivate The antivirus and/or firewall will run for a few minutes. (Be very careful, do this only to test) and start the game. If everything suddenly works perfectly, you know the problem lies with those security tools. The next step will be to create a exception for the game executable and, if necessary, open the ports indicated in the developer's documentation.

Another important point is to maintain everything updatedOperating system, game, antivirus, network drivers, etc. An old game with an outdated system and a recent antivirus is the perfect recipe for strange conflicts, crashes, and compatibility errors.

We also need to keep an eye on the add-ons or mods of the game, especially if they are not official. They can trigger alerts in both the antivirus and the game itself (because it thinks you are cheating), causing you to be blocked from the game or even... your account will be bannedIf the problem started right after installing a mod, uninstall it to see if it was the cause.

VPN, Security Center and Firewall Detection

The VPN They add another layer of complexity. When you browse behind a VPN (especially a free one), it's common for the connection to become unstable and for antivirus software or firewalls to see that traffic as more suspicious, causing outages or slowdowns.

If you notice that everything goes wrong only when you have the VPN active, but It works fine when you turn it off.The conflict likely lies in the interaction between the VPN and your security suite. Generally, it's advisable to avoid free VPNs for gaming or sensitive applications, both for security and performance reasons.

On the other hand, the Action Center / Windows Security Center It relies on WMI to determine which antivirus and firewall are active. If the WMI repository is corrupted or the WMI service fails to start correctly, it may show that the Windows Firewall is off, or that your antivirus is disabled, even if the application itself indicates otherwise.

In those cases, if you see that Windows insists your computer is not protected but, when you open the antivirus, everything seems fine, check if you need repair the WMI repository following the security provider's instructions, before making any further changes to the firewall.

In managed teams, it is also important to consider that the organization can impose directives They might disable the Windows Firewall and force you to use another one, or they might block certain changes you're trying to make. If clicking "Activate" does nothing, it's possible your company has disabled it centrally.

When all of this comes together, distinguishing whether the problem comes from Windows Defender Firewall, a third-party firewall, the router, or the antivirus seems like a mess, but, if you follow a logical order (check the actual status of the firewall, review rules and ports, look at logs and services, briefly try disabling components and note when the error disappears), you can narrow down the source of the failure quite well and adjust it without giving up the protection that these tools provide.