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Brute Force Attack
Table of Contents
This ethical hacking guide explains what a brute force attack is, the tools and techniques used to brute force a password, and its prevention in cyber security.
What is Brute Force Attack?
Brute force attack is a malicious technique in which an attacker tries all possible combinations of passwords or other data to gain unauthorized access to a system or decrypt encrypted data.
This method relies on computational power rather than exploiting software vulnerabilities and can be time-consuming and resource-intensive. Brute force attacks are often used by hackers to exploit weak or easily guessable passwords and gain unauthorized access to a target, such as an online account, computer system, or network.
Types of Brute Force Attacks
These can be classified into two types based on the mode used (online/offline):
1. Offline Brute Force Attack
In an offline attack, attackers have access to a copy of the authentication database (for example, hashed passwords), but do not need to interact directly with the target system or service. They can use this data to carry out attacks without being detected or locking the account.
2. Online Brute Force Attack
In an online attack, the attacker attempts to gain access to a system or account by directly interacting with the target's login page. These attacks can be detected and countered through various security measures.
How to Brute Force a Password?
Here are the steps commonly followed by an attacker to crack a password using brute force technique:
Step-1: Target Identification
The attacker selects a target, such as a system, an online account, or an encrypted file, that requires a password or encryption key for access.
Step-2: Password/Key Generation
The attacker generates a list of potential passwords or encryption keys to try. This list can be created by various means, such as using a dictionary of common passwords, combining words, trying variations of known information about the target, or generating random combinations.
Step-3: Iterative Attempt
The attacker uses automated software or scripts to systematically try each password from the generated list. They input the password into the login or authentication form of the target account or system.
Step-4: Validation
After each attempt, the system or encryption algorithm checks whether the entered password or key is correct. If it matches, the attacker successfully gains access to the system or decrypts the data.
Step-5: Iteration
If the attempted password or key is incorrect, the attacker moves on to the next password/key in the list and repeats the process until either the correct password/key is found or the entire list is exhausted.
Tools and Techniques
Tools:
Some of the most commonly used tools for brute force attacks include:
1. Hydra
Often used to crack login forms, Hydra can perform rapid dictionary or brute force attacks against more than 50 protocols, including telnet, ftp, http, https, smb, several databases, and more.
2. Hashcat
Known for its speed and versatility, Hashcat supports many algorithms and is considered one of the fastest password cracking tools. It can utilize the power of both CPUs and GPUs to speed up the cracking process.
3. Brutus
A popular remote online password cracker for Windows, Brutus is known for its ability to perform brute force attacks on web services like FTP, POP3, and HTTP.
Techniques:
Techniques used in brute force attacks vary based on complexity and purpose:
1. Simple Brute Force
In this approach, attackers use a trial-and-error method to guess the login info, trying every possible combination of characters. This method is straightforward but can be extremely time-consuming and is generally effective only against weak security systems or short passwords.
2. Dictionary Attack
Rather than trying every combination of characters, attackers use a dictionary of words (which could include common passwords and phrases) to attempt to log in. This method is faster than a simple brute force attack because it relies on the likelihood that many users choose common words or simple variations of them as passwords.
3. Rainbow Table Attack
Instead of trying all combinations, attackers use precomputed tables called rainbow tables which contain the hashes of many possible password combinations. It is faster than traditional brute force but less effective against systems with strong hashing and salting.
4. Credential Stuffing
This is a type of brute force attack where stolen account credentials (usernames and/or email addresses and passwords) from a breach are used to gain unauthorized access to user accounts on different websites, under the assumption that many people reuse usernames and passwords across multiple sites. Tools like "SNIPR" or "Sentry MBA" automate this process.
Prevention Methods
To prevent brute force attacks and enhance the security of your systems, there are several measures you can implement:
1. Strong Password Policies
Enforce strong password policies that require users to create passwords with a combination of uppercase and lowercase letters, numbers, and special characters. Encourage regular password updates and avoid easily guessable passwords.
2. Account Lockouts and Delays
Implement mechanisms that lock user accounts or introduce delays after a certain number of failed login attempts. This prevents attackers from repeatedly attempting different passwords within a short period.
3. CAPTCHA or Turing Tests
Incorporate CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) or other Turing tests to differentiate between humans and automated bots. These tests help prevent brute force attacks by making it difficult for automated scripts to repeatedly submit login attempts.
4. Multi-Factor Authentication (MFA)
Implement multi-factor authentication, which requires users to provide additional verification beyond passwords. This can include one-time passwords, biometric authentication, or hardware tokens. MFA adds an extra layer of security, making it significantly more challenging for attackers to gain unauthorized access.
5. Rate Limiting
Employ rate limiting techniques to restrict the number of login attempts allowed within a specific time frame. By imposing limitations on the frequency of login requests, you can prevent rapid and successive brute force attempts.
6. Encryption and Strong Algorithms
Use encryption for sensitive data, employing strong encryption algorithms and key lengths. This ensures that even if an attacker gains access to the data, it remains unreadable without the encryption key.
Summary
The success of a brute force attack depends on the length and complexity of the password or encryption key, as well as the computational power available to the attacker. Longer and more complex passwords or keys increase the time required for the attack, while stronger computational resources decrease the time needed to test each combination.