How does a brute force password attack work?

Compromising login credentials is the goal of many modern cyber-attacks. If successful, they can result in the worst types of data breaches, especially when high-level accounts are breached. One of the oldest and most common methods for guessing a user’s password is the brute force attack. We’ll explore what they are, how they work, and how organizations can defend against them.

What are brute force attacks?

Brute force attacks are relatively straightforward to understand. They’re essentially an unsophisticated yet highly effective method of decoding encrypted data such as passwords. Cybercriminals use tools to test all possible password combinations through countless login attempts until the correct one is identified. The more computing power they have, the faster this process becomes – especially if weak passwords are involved.

However, not all brute force attacks are the same. Cybercriminals employ a range of tactics from simple brute force attacks, which test every possible password combination, to more nuanced approaches such as the hybrid and reverse brute force attacks. Each method has a distinct strategy behind it, but the motives behind brute force attacks are the same – cracking passwords to gain unauthorized access to protected information.

Types of brute force attacks

The nuances between these types of attack highlight the evolving sophistication of cybercriminals and underscore the need for staying on top of your defensive measures.

  • Simple brute force attacks: Attackers use a systematic trial-and-error method to guess password combinations. This type of attack is exhaustive and can be time-consuming, but it’s effective if the target has weak cybersecurity measures in place.
  • Dictionary attacks: Involves attempting all the words in a pre-defined list or “dictionary” of common passwords. Dictionary attacks exploit users’ tendencies to use simple, easily remembered (and easily guessed) passwords. They can be highly effective against organizations who have failed to implement strong password policies.
  • Reverse brute force attacks: Instead of trying many passwords for one user, the attacker tries a common password with many different usernames within an organization. This type of attack capitalizes on users often going for the same weak passwords, meaning it’s likely to have been chosen by at least one person.
  • Hybrid brute force attacks: Combines elements of both dictionary and simple brute force attacks, using a dictionary of passwords but with added numerical or special character combinations.

Real-world example of a brute force attack

In August 2021, T-Mobile, one of the largest wireless network operators in the US, fell victim to a substantial cybersecurity breach traced back to a brute force attack. The incident led to the exposure of sensitive personal data of over 37 million past, present, and prospective customers. The stolen data included social security numbers, driver’s license information, and other personally identifiable data.

This incident highlighted the vulnerability of even major organizations to brute force attacks and reinforced the need for robust cybersecurity measures. Even though passwords are encrypted and stored as password hashes, attackers can still “guess” the passwords until they successfully match the password represented by the password hash.

Preventing brute force attacks

There are several preventative cybersecurity measures that organizations should be using in collaboration to lower the risk of being caught out by a brute-force attack.

Longer passwords

By increasing password length and incorporating a mix of uppercase and lowercase letters, numbers, and special characters, the number of possible passwords skyrockets, making brute force attacks exponentially more challenging – even with large amounts of computing power. The best way create a long password over 20 characters is through a passphrase where three random memorable words are strung together with a few lesser used special characters incorporated.

Unsure how many people in your organization are using weak or compromised passwords? Run a free audit today with Specops Password Auditor for a full picture of your password risks.  

Multi-factor authentication

Implementing multi-factor authentication (MFA) is another effective strategy for combating brute force attacks. By requiring users to verify their identity through a secondary method, such as a mobile app or a text message code, MFA dramatically reduces the likelihood of unauthorized access, even if a password is compromised.

Monitor for unsuccessful login attempts

Monitoring for multiple unsuccessful login attempts can also serve as an early warning sign of a brute force attack in progress. Many systems implement account lockout or delay policies after a certain number of failed login attempts, preventing further attempts, and effectively thwarting simple brute force attacks.

Secure your systems against brute force attacks with Specops

While these measures can significantly bolster defenses against brute force attacks, managing them can be a daunting task for IT Security teams. Specops Password Policy enhances security by preventing users from choosing common password patterns and continuously scanning for known breached passwords, making it exponentially harder for a brute force attack to be successful. The Breached Password Protection feature references a list of over 4 billion compromised passwords, even those being used in attacks right now.

Specops Breached Password Protection

Specops Password Policy also comes with a helpful end user interface to guide employees on creating longer, stronger passphrases that meet your organization’s password policy requirements. Try Specops Password Policy for free today and secure your users against brute force attacks.

Specops Password Policy: Passphrase settings

(Last updated on July 17, 2023)

brandon lee writer

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Brandon Lee

Brandon Lee has been in the industry 20+ years, is a prolific blogger focusing on networking, virtualization, storage, security & cloud, and contributes to the community through various blog posts and technical documentation primarily at

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