Password Cracking: The Three Most Dangerous Attack Methods and How to Protect Yourself
The importance of passwords is often overlooked—until a data breach occurs. In other words, nothing highlights the necessity of a strong password more than the consequences of a weak one. However, most end users are unaware of how vulnerable their passwords are to common attack methods. Below, we explain three widespread password-cracking techniques and how to defend against them.
Brute-Force Attack
Brute-force attacks are a simple yet highly effective method of cracking passwords. Attackers use automated tools to systematically try every possible password combination until they find the correct one. Advances in computing power and storage technology have made these attacks more efficient than ever—especially against weak passwords.
How It Works
Attackers employ various brute-force techniques, ranging from simple methods that test every possible character combination to hybrid or inverse brute-force attacks that specifically target known passwords or variations thereof. While the approaches differ, the goal is always the same: unauthorized access to protected data or systems.
Popular brute-force automation tools include:
- John the Ripper:: A cross-platform password-cracking tool that supports 15 different operating systems and hundreds of hash and cipher types.
- L0phtCrack: Uses rainbow tables, dictionaries, and multi-threaded algorithms to crack Windows passwords.
- Hashcat: A powerful password-cracking and recovery tool with five attack modes and support for over 300 optimized hash algorithms.
Examples
In August 2021, the U.S. branch of the mobile carrier T-Mobile suffered a data breach that began with a brute-force attack. As a result, more than 37 million confidential customer records were exposed, including Social Security numbers, driver’s license details, and other personal data.
Protection Measures
Users should create complex, secure passwords and enable multi-factor authentication (MFA) to protect against brute-force attacks. Administrators should implement account lockout mechanisms after repeated failed login attempts and continuously monitor Windows environments for weak or compromised passwords. Tools like Specops Password Auditor can automate these processes across large IT infrastructures.
Dictionary Attack
In a dictionary attack, cybercriminals use lists of commonly used passwords or dictionary words to gain access to an account or system. These lists typically contain frequently used passwords and simple combinations like “admin123.” Dictionary attacks emphasize the importance of using complex and unique passwords, as they are particularly effective against weak or easily guessable passwords.
How It Works
First, attackers compile a list of potential passwords based on data breaches, commonly used password lists, or publicly available resources. Automated tools then systematically test each password on a target account or system. Once a match is found, the attacker gains access and can proceed with further attacks or malicious actions.
Examples
Dictionary-based methods have been used in some of the largest data breaches in history to crack hashed passwords, including the 2013 Yahoo data breach and the 2012 LinkedIn breach. These incidents exposed the information of billions of user accounts.
Protection Measures
When creating or resetting passwords, users should use a mix of letters, numbers, and special characters and avoid common words or easily guessed phrases. Administrators should enforce policies requiring passwords to meet specific complexity criteria within their organization.
Rainbow Table Attack
A rainbow table attack leverages precomputed tables (“rainbow tables”) containing frequently used character sequences and their corresponding hashes to decrypt password hashes stored in a database.
How It Works
Rainbow table attacks use chains of hashing and reduction operations to crack hashed passwords. First, possible passwords are hashed and stored alongside their plaintext equivalents in the rainbow table. Then, a reduction function processes them, mapping them to new values, creating a chain of hashes. This process is repeated multiple times to generate the rainbow table. When hackers obtain a list of password hashes, they can look up each hash in the rainbow table. If a match is found, the corresponding plaintext password is revealed.
Examples
Although salting (adding random characters to passwords before hashing) reduces the effectiveness of rainbow table attacks, many hashes remain unprotected. Advances in GPU technology and affordable hardware have also eliminated previous storage limitations, making rainbow table attacks a continued threat in modern and future cyberattacks.
Protection Measures
As mentioned, salting hashes has significantly weakened precomputed table attacks. Organizations should implement strong hash algorithms (such as bcrypt or scrypt) in their password processes. Additionally, administrators should enforce regular password updates and rotation policies to reduce the likelihood of a successful rainbow table attack.
Conclusion
No password is ever entirely secure, but long and complex passphrases remain a critical defense against advanced password-cracking methods. Tools like Specops Password Policy provide additional protection by continuously comparing Active Directory environments against a database of over four billion compromised passwords. Contact us today for a free demo.
