What is a Brute Force Attack?

Back to learning

Brute force attacks are a straightforward method of compromising user accounts and systems by systematically attempting all possible combinations of login credentials. These attacks are often enhanced by tools designed to streamline the process, and advanced attackers even use techniques to avoid detection.

How Brute Force Attacks Work

Attackers use specialized software tools to automate the brute force process, applying various methods to guess passwords:

1. Dictionary Attacks: Uses a list of known words.
2. Simple Brute Force: Tries all combinations of characters.
3. Hybrid Brute Force: Combines dictionary words with numerical and symbolic variations.
4. Rainbow Table Attacks: Utilizes precomputed tables to expedite password cracking.

Common Tools

1. John the Ripper: Supports various password hash algorithms.
2. Hashcat: Known for speed and supports a variety of hashing algorithms.
3. Hydra: Flexible and useful for attacking multiple protocols.
4. Crunch: A wordlist generator.
5. Aircrack-ng: Used for cracking wireless network keys.

Evasion Techniques

Attackers use several strategies to avoid detection while executing brute force attacks:

1. IP Rotation: By regularly changing their IP address, attackers make it more difficult for security systems to identify and block them.
2. Residential Proxies: Hiding requests in residential networks makes it difficult to identify and block.
3. User-Agent Spoofing: Mimicking different browser user-agents can help attackers bypass security measures.
4. Time Delays: Introducing random delays between login attempts can avoid tripping rate-limiting security measures.
5. Distributed Attacks: Conducting the attack from multiple machines can spread the load, making it harder to detect.
6. Traffic Obfuscation: Encrypting attack traffic or routing it through multiple proxies can disguise the attack’s origin.

Targets and Goals

Brute force attacks can target different types of authentication:

1. Web Logins: Unauthorized access to web applications.
2. SSH Servers: Cracking SSH to control systems.
3. FTP Servers: Access to FTP servers to manipulate files.
4. Email Accounts: Compromising email accounts.

Objectives

1. Data Theft: Accessing and stealing data.
2. Resource Utilization: Using compromised systems for other illegal activities.
3. Service Disruption: Overloading systems to make them unresponsive.
4. Fraud: By taking over an existing account attackers may use it to commit fraud.

Defensive Measures

1. Account Lockout: Locking accounts after failed login attempts.
2. Multi-Factor Authentication: Make logging in more difficult by requiring a second piece of information.
3. Rate Limiting: Limiting the number of login attempts within a specific timeframe.
4. Bot Management: Use bot management tools to recognise and block automated attempts to login.
5. Web Application Firewall: Block known attackers from accessing your system.