How to Prevent Brute Force Attacks Against Your Firewall

Key Takeaways

• Brute force attacks repeatedly test passwords or stolen credentials until an attacker gains access.
• Firewalls, virtual private networks, remote desktop services, and other internet-facing systems are common targets.
• Multi-factor authentication, trusted IP restrictions, rate limiting, and secure password policies can prevent many attacks.
• Geo-IP filtering can reduce unnecessary exposure, but it should not be your only security control.
• Continuous monitoring helps your team detect password spraying, unusual login locations, and repeated authentication failures.
• Your strongest defense combines technology, configuration management, identity security, and clear response procedures.

Brute force attack prevention requires more than a strong firewall. Your organization must protect every internet-facing login point with layered identity, access, monitoring, and response controls.

Attackers routinely target firewalls, virtual private network portals, Remote Desktop Protocol services, and administrative interfaces because these systems can provide direct access to your network. If your defenses rely primarily on passwords, automated tools may test thousands of credential combinations or reuse credentials exposed in previous breaches.

Related: Firewall Upgrades That Increase Protection Against Cyber Threats

The right controls can sharply reduce this risk. This guide explains how brute force attacks work, why they matter, and how you can strengthen your firewall and remote access environment.

What Is a Brute Force Attack?

A brute force attack is an attempt to gain unauthorized access by repeatedly testing usernames, passwords, passphrases, or other authentication credentials.

Attackers often automate the process using scripts, botnets, or compromised devices. Rather than manually entering credentials, they can perform large numbers of login attempts across one account, many accounts, or several public-facing systems.

Common variations include:

• Traditional brute force: Testing many password combinations against a specific account.
• Dictionary attacks: Trying passwords drawn from lists of common words and known patterns.
• Password spraying: Testing a small number of common passwords across many accounts.
• Credential stuffing: Reusing username and password combinations obtained from previous data breaches.

These techniques differ, but they exploit the same weakness: an authentication system that allows attackers to make repeated or poorly controlled login attempts.

How Do Brute Force Attacks Target Firewalls?

A firewall brute force attack typically begins with reconnaissance. Attackers scan public IP addresses to identify exposed ports, remote access portals, and administrative services.

Related: Why Old Firewalls Are No Match For New Threats

Attackers search for exposed services

Secure Sockets Layer virtual private networks, Remote Desktop Protocol, Secure Shell, and web-based firewall management portals may be discoverable from the internet.

An open port is not automatically a vulnerability. However, every exposed service increases your attack surface and must be configured, patched, and monitored carefully.

Automated tools test credentials

Once a login page is identified, attackers may use automated tools to submit large volumes of credential combinations.

Weak passwords, default credentials, reused passwords, and inactive accounts make successful access more likely. Attackers may also distribute attempts across many IP addresses to avoid simple blocking rules.

Password spraying avoids account lockouts

Traditional lockout policies can detect repeated attempts against one account. Password spraying works differently by testing one likely password against many users.

Because each account receives only a few attempts, the activity may remain below standard lockout thresholds.

Misconfigurations make access easier

Brute force attacks become more dangerous when a firewall or remote access system has:

• Internet-accessible administrative interfaces
• Default or unnecessary accounts
• Weak authentication requirements
• Broad geographic availability
• Outdated firmware or software
• Limited logging and alerting
• No restrictions on repeated login attempts

After gaining access, an attacker may attempt to move deeper into your environment, create new accounts, change security policies, install malware, or establish persistent remote access.

Why Does Brute Force Attack Prevention Matter?

A successful firewall login can expose more than one device. It may give an attacker a pathway into systems, cloud resources, user accounts, confidential data, and business-critical applications.

Potential consequences include:

• Data theft or encryption
• Business interruption
• Unauthorized configuration changes
• Fraudulent activity
• Malware deployment
• Compliance exposure
• Incident response and recovery costs
• Loss of customer or stakeholder trust

Prevention is especially important for organizations with remote employees, distributed offices, third-party access, limited internal security staffing, or critical systems connected to public-facing infrastructure.

How Can You Prevent Brute Force Attacks?

The most effective strategy uses multiple controls. No single tool can address every attack method.

1. Require Multi-Factor Authentication

Multi-factor authentication requires users to provide an additional form of verification beyond a password.

Even when attackers obtain or correctly guess a password, the additional authentication factor can stop them from completing the login.

Your organization should prioritize multi-factor authentication for:

• Firewall administrators
• Virtual private network users
• Remote desktop access
• Cloud administrators
• Privileged accounts
• Third-party support accounts

Phishing-resistant authentication methods provide stronger protection than easily intercepted codes when your systems support them.

2. Restrict Access to Trusted IP Addresses

Trusted IP restrictions allow access only from approved networks, office locations, secure gateways, or authorized administrative addresses.

This control is especially useful for management interfaces that do not need to be available to the general public.

Your team should also remove unnecessary internet-facing services and use secure administrative pathways instead of exposing management portals directly.

3. Use Geo-IP Filtering Carefully

Geo-IP filtering blocks or restricts traffic based on its apparent geographic origin.

If your employees and partners operate only in specific regions, filtering can reduce unwanted login traffic from locations with no legitimate business need.

However, attackers can use proxies, virtual private networks, and compromised systems to disguise their location. Geo-IP filtering should support your broader security strategy, not replace multi-factor authentication or monitoring.

4. Apply Rate Limiting and Login Controls

Rate limiting restricts the number or speed of authentication attempts.

Useful protections include:

• Progressive delays after failed logins
• Temporary account or source blocking
• Connection throttling
• Alerts for repeated failures
• Risk-based authentication challenges

Account lockouts should be configured carefully. Overly aggressive settings may allow attackers to intentionally lock out legitimate users.

5. Strengthen Password and Account Management

Require long, unique passwords and prohibit default or commonly compromised credentials.

You should also:

• Disable inactive accounts
• Remove unnecessary local administrator accounts
• Review third-party access regularly
• Use separate administrative credentials
• Prevent password reuse where practical
• Store privileged credentials in an approved password manager

Strong password practices make credential guessing more difficult and limit the value of credentials exposed elsewhere.

6. Monitor Authentication Activity

Monitoring helps your team identify activity that preventive controls do not stop.

Watch for:

• Large numbers of failed logins
• Attempts against many accounts
• Logins from unusual regions
• Authentication at unexpected times
• New administrative sessions
• Sudden changes in firewall policies
• Successful logins following repeated failures

Your alerting process should identify who investigates the activity, how quickly it must be reviewed, and when access should be disabled.

Related Webinar: Taming the Cyber Threat Landscape

What Should You Do After Detecting an Attack?

First, preserve relevant firewall, authentication, endpoint, and network logs. Then block malicious sources where appropriate and determine whether any login attempt succeeded.

Your response should also include:

• Resetting affected credentials
• Revoking active sessions
• Reviewing administrative changes
• Checking for new accounts or persistence
• Examining connected systems for suspicious activity
• Correcting the configuration weakness that enabled the attack
• Documenting the event and lessons learned

Blocking one IP address is rarely a complete response because distributed attacks can shift quickly to other sources.

Strengthen Firewall Security With a Layered Approach

To prevent brute force attacks, your organization must reduce unnecessary exposure, strengthen authentication, restrict access, and monitor behavior continuously.

Multi-factor authentication, trusted IP restrictions, geo-IP filtering, rate limiting, secure passwords, and timely alerting each solve a different part of the problem. Together, they create a more resilient defense for your users, your firewall, and your wider network.

In Logically’s webinar, VP of Cybersecurity Zack Finstad and Network Security Manager Kyle Sandy explain how multi-factor authentication, geo-IP filtering, zero-trust practices, and secure remote access can help defend your organization against brute force attacks and related cyber threats.

Last updated July 2026

FAQs

What is the best way to prevent brute force attacks?

The strongest approach combines multi-factor authentication, rate limiting, access restrictions, strong passwords, account management, and continuous login monitoring.

Can a firewall stop brute force attacks automatically?

A properly configured firewall can block or slow suspicious activity, but it cannot eliminate every credential-based attack. Identity controls and monitoring are also required.

What is the difference between brute force and password spraying?

A brute force attack usually tests many passwords against one account. Password spraying tests a few common passwords across many accounts to avoid lockouts.

Does multi-factor authentication stop brute force attacks?

Multi-factor authentication can prevent a guessed or stolen password from being enough to access an account. It is one of the most important controls for remote and privileged access.

Is geo-IP filtering enough to secure a firewall?

No. Geo-IP filtering can reduce exposure, but attackers may disguise their locations. It should be combined with multi-factor authentication, IP restrictions, rate limiting, and monitoring.

Which systems are commonly targeted by brute force attacks?

Common targets include virtual private network portals, Remote Desktop Protocol services, Secure Shell services, email accounts, cloud applications, and firewall administration interfaces.

How can you detect password spraying?

Look for failed login attempts across many accounts, especially when the same password pattern, source infrastructure, location, or time window appears repeatedly.

Should firewall management interfaces be exposed to the internet?

Whenever possible, management interfaces should be limited to trusted IP addresses, secure administrative networks, or controlled remote access pathways.