What is a brute force attack?

Brute force attack: How hackers crack passwords

Brute force attacks are among the oldest and most common techniques used by cybercriminals. While the method may seem basic, it remains highly effective, especially against systems with weak passwords or poor security measures.

Brute force attacks remain a prevalent and ongoing threat, making it essential for organizations to stay vigilant and implement robust security practices.

At their core, brute force attacks rely on computational power and persistence to systematically try all possible password combinations until they succeed.

What is a brute force attack?

A brute force attack is a hacking technique where attackers systematically guess login credentials, encryption keys, or hidden information by trying every possible combination. The number of possible combinations can be vast, as attackers attempt to cover all possible passwords, including those that are common, predictable, or derived from data breaches. The goal is to eventually guess the correct password or key through repetition.

These attacks are typically automated using software that can test millions of combinations in a short time. Brute force attacks involve numerous password attempts, which can be automated to rapidly test possible passwords and increase the chances of success. This makes brute force attacks a persistent threat to both individuals and organizations.

How brute force attacks work

The purpose of a brute force attack is to gain unauthorized access to a user account, network, or encrypted data. Once access is obtained, attackers can steal sensitive information, install malware, or escalate the attack further. Compromised accounts, especially user accounts with elevated privileges, can serve as entry points for larger security incidents, increasing the risk of data theft, further breaches, and the spread of malware.

The process usually follows these steps:

1. Identifying a target The attacker selects a specific target system or target server, such as an account, web application login, or encrypted file, to breach.

2. Gathering information Hackers collect public or leaked data to improve the chances of success.

3. Launching the attack Automated tools are used to generate and test a wide range of password combinations. Attackers start by trying common passwords or known words before moving to more complex password attempts.

4. Gaining access When the correct credentials are found, the attacker enters the system.

5. Exploitation The attacker may steal data, install malware, or use the access to target additional systems.

Common types of brute force attacks

There are several variations of brute force attacks, each with a slightly different approach. Many passwords are vulnerable to brute force password attacks, especially when users choose weak or reused credentials.

1. Simple brute force attack

Simple brute force attacks involve manually trying to guess passwords by systematically attempting all possible combinations, often starting with common words, names, or phrases.

A six-character password can be cracked very quickly using simple brute force attacks, especially with the power of modern hardware.

2. Dictionary attack

Instead of testing every possible combination, the attacker uses a predefined list of commonly used passwords. Variants like “Password1” or “Qwerty2023” are frequently tested.

3. Hybrid attack

This method combines a dictionary attack with a traditional brute force attack. The attacker starts with known words and then adds random characters, including upper and lowercase letters, to create more complex and effective password guesses. This blending of techniques increases the chances of success.

4. Reverse brute force attack

In reverse brute force attacks, the attacker starts with a known password or password pairs and tests them across a large number of usernames. This method is often based on leaked password databases.

5. Credential stuffing

Credential stuffing is an attack that exploits the use of the same credentials across multiple sites. Hackers use stolen username and password combinations from previous data breaches and test them on other websites. This is highly effective because many users reuse the same password for multiple accounts, increasing their vulnerability to credential stuffing attacks.

Online vs. offline brute force attacks

Online brute force attacks are a type of online attacks that target live systems in real time, relying on repeated login attempts. Attackers often focus on services like remote desktop protocol (RDP), which has become a common target due to increased remote work. These attacks are often slowed down or blocked by security features such as CAPTCHA, login attempt limits, and multi-factor authentication.

Offline brute force attacks typically occur after a data breach, where an attacker obtains encrypted password files or password hashes. The attacker then tries to crack them without interacting with a live system. These attacks are often faster and harder to detect.

Authentication systems and their role in brute force defense

Authentication systems are the first line of defense against brute force attacks. These systems are designed to verify that only legitimate users gain access, making it much harder for attackers to succeed with brute force attempts. By enforcing complex passwords and limiting the number of failed login attempts, authentication systems can significantly reduce the likelihood of a successful brute force attack.

Modern authentication systems often incorporate multi-factor authentication, requiring users to provide additional proof of identity beyond just a password. This extra layer makes it nearly impossible for attackers to gain access through brute force alone. Additionally, advanced authentication systems can detect unusual login attempts in real time, such as a sudden spike in failed login attempts, and alert security teams to take immediate action. By combining these features, authentication systems play a crucial role in stopping brute force attacks before they can compromise sensitive data or user accounts.

Why hackers use brute force attacks

Brute force attacks may require time and computing power, but the potential rewards make them worthwhile for many attackers. They use brute force methods to:

• Steal personal and financial data

• Install malware such as spyware, ransomware, or trojans

• Sell login credentials on underground forums

• Gain access to business networks and cause service disruptions

• Launch larger cyberattacks from compromised systems

• Leverage compromised social media accounts to distribute automated login attacks or mask malicious login attempts

Common brute force tools and techniques

Cybercriminals use a variety of tools to automate brute force attacks:

• Aircrack-ng is commonly used for testing Wi-Fi security

• John the Ripper is a powerful tool for cracking different types of password hashes

• THC Hydra is designed for testing remote logins such as SSH, FTP, and Telnet

• Rainbow table attacks use precomputed tables of hash values to efficiently crack passwords, especially for hashing algorithms like MD5 and SHA-1

The effectiveness of brute force tools depends on the size of the key space, as a larger key space means more potential keys must be tested, making the attack more difficult.

Hardware acceleration

To speed up brute force attacks, hackers often use graphics processing units (GPUs). Unlike CPUs, which perform tasks one at a time, GPUs can process thousands of operations simultaneously. This can reduce the time to crack a password from months to just hours.

Some attackers also use botnets or custom hardware like field-programmable gate arrays (FPGAs) to increase attack speed by distributing the workload across multiple devices. Explore how botnets operate and why they are a major cybersecurity threat.

Advanced threats: Evolving brute force techniques

Brute force attacks are no longer limited to simple, repetitive password guessing. Today’s cybercriminals are leveraging advanced tactics, such as hybrid brute force attacks, which blend traditional brute force methods with techniques like phishing and social engineering. These hybrid brute force attacks are more targeted and adaptive, making them harder to detect and defend against.

Attackers are also using artificial intelligence and machine learning to analyze password policies and user behavior, allowing them to optimize their brute force strategies and increase their chances of success. As brute force attacks evolve, security teams must stay vigilant and continuously update their defenses. This includes monitoring for new types of brute force attacks, deploying advanced detection tools, and regularly reviewing security protocols to ensure they are prepared for the latest threats.

Why weak passwords are a risk

Weak passwords make brute force attacks much easier. Common password mistakes include:

• Using personal information such as names or birthdates

• Choosing short or simple passwords

• Reusing passwords across multiple accounts

• Avoiding complexity by only using letters or numbers

These practices make it significantly easier for attackers to succeed. It is essential to use strong, unique passwords for each account and avoid predictable patterns. Using longer passwords – ideally at least 12 to 15 characters – and strong passwords that combine upper and lowercase letters, numbers, and special characters greatly reduces the risk of brute force attacks. Learn how to create a strong password to protect your accounts.

How to prevent brute force attacks

1. Create strong, unique passwords

• Use at least 12 characters

• Combine uppercase and lowercase letters, numbers, and symbols

• Avoid obvious choices like "123456" or "admin"

• Use a password manager to generate and store secure passwords

2. Enable multi-factor authentication (MFA)

MFA adds an extra layer of security by requiring users to verify their identity using a second method, such as a code sent via SMS or a biometric scan. Even if an attacker guesses the password, they cannot access the account without the second factor.

3. Limit login attempts and use account lockout policies

Limit the number of login attempts to reduce the risk of automated guessing. Lock accounts temporarily after multiple failed attempts to stop brute force tools from running indefinitely.

4. Use CAPTCHA and IP blocking

CAPTCHA challenges help distinguish between humans and bots. Blocking suspicious IP addresses can stop attackers before they gain access.

5. Secure password storage

Passwords should always be stored using strong encryption and hashing. Adding a unique "salt" to each password before hashing makes them even harder to crack if the database is leaked.

6. Monitor login behavior

Set up real-time monitoring and alerting for suspicious login activity. Intrusion detection systems (IDS) can help identify brute force attempts early.

7. Remove unused accounts

Inactive accounts can be easy targets for attackers. Regularly review and delete accounts that are no longer in use.

Security awareness: Educating users and teams

Building a strong defense against brute force attacks starts with security awareness. Educating users and security teams about the dangers of brute force attempts and the importance of using complex passwords can make a significant difference. Users should be trained to avoid common passwords, recognize suspicious login activity, and enable multi-factor authentication on all accounts.

Security teams should also be equipped to identify and respond to brute force attacks, such as monitoring for unusual login attempts or blocking suspicious IP addresses. By fostering a culture of security awareness, organizations can reduce the risk of a successful brute force attack and empower everyone to play a role in protecting sensitive data and user accounts.

Incident response: What to do if you’re targeted

If your organization becomes the target of a brute force attack, having a clear incident response plan is essential. The first step is to detect the attack by monitoring login attempts and identifying patterns that indicate a force attack, such as a high volume of failed logins from the same IP address. Once detected, immediately block the offending IP addresses to prevent further brute force attempts.

Next, assess the impact by reviewing system logs and determining whether any accounts or sensitive data have been compromised. Notify affected users and require password resets if necessary. Finally, strengthen your defenses by updating password policies, enabling multi-factor authentication, and providing additional security awareness training. By acting quickly and methodically, you can minimize the damage from a brute force attack and better protect your organization in the future.

Conclusion

Brute force attacks continue to be a major cybersecurity threat. While they may seem simple, their potential impact is significant. The best defense is a proactive one.

By understanding how brute force attacks work and taking steps to strengthen password security, implement multi-factor authentication, and monitor systems actively, both individuals and organizations can significantly reduce their risk of being compromised.