Describe how a password cracking attack can be successfully launched and what countermeasures should be implemented.

A password cracking attack is a method used to recover passwords, often for unauthorized access to systems or data. The success of such an attack relies on exploiting vulnerabilities in password creation, storage, or transmission mechanisms. These attacks aim to break the hashed or encrypted representation of passwords and recover the actual passwords that users have set. Password cracking can be performed offline or online, with each approach having distinct characteristics. Offline attacks typically involve obtaining a database of password hashes and attempting to crack them on dedicated systems without interacting directly with the target system. This approach is often faster and can use resources more efficiently. Online attacks, on the other hand, target live systems by repeatedly attempting logins. These attacks require interaction with the target, making them less stealthy and more prone to detection.

Several techniques are used to launch password cracking attacks, and understanding them helps in implementing adequate security measures. A common attack is the dictionary attack, which involves using a pre-compiled list of common passwords to match against password hashes. For example, a hacker might download a large password list that contains millions of common passwords and then try each one against hashed passwords of user accounts. Brute-force attacks involve trying every possible combination of characters until a matching password is found. These attacks are effective against weak passwords but are computationally intensive and take longer to complete. For example, a brute-force attack tool could start trying every combination of upper- and lower-case letters, numbers, and symbols. Hybrid attacks combine dictionary and brute-force approaches, adding variations and numbers to dictionary words to crack more complex passwords. Rainbow tables are pre-computed tables that are often used to speed up the process of cracking password hashes by storing pre-calculated hash values. Hash collision attacks are used when hashes are not unique and different passwords resolve to the same hash. This is less common with modern hashing algorithms, but still possible with older, less robust algorithms.

For example, if an attacker managed to steal a database of hashed passwords from a website that was using a weak hashing algorithm like MD5, they could then use rainbow tables to try and crack those password hashes and gain access to user accounts. If an attacker manages to gain access to the file containing user credentials on a server which may not be properly protected, they can then start the process of password cracking by performing an offline cracking attack with hashcat or john the ripper. Another type of attack may involve the use of password spraying, where a list of usernames is paired with a list of common passwords across different websites and services.

To counter password cracking attacks, several strategies must be implemented to strengthen password security. Password complexity policies that enforce the use of a mix of upper and lower-case letters, numbers, and special characters are essential, which makes brute-force attacks more time-consuming. Password length requirements should also be enforced since shorter passwords are easier to break. For example, organizations should require that passwords be longer than 12 characters and should have a complex mixture of different characters. Salting password hashes, which involves adding a random string to the password before hashing, makes precomputed tables less effective. For example, each user would have their own unique random salt string added to their passwords before being hashed. Using strong hashing algorithms like SHA-256, SHA-512, or bcrypt is crucial for slowing down cracking attacks and making it computationally difficult to obtain original passwords. Multi-factor authentication (MFA), which requires more than just a password for login, is also vital in mitigating password cracking attacks. For example, in addition to using a password for login, a user would also need to use a second factor such as a code sent to their mobile phone or a fingerprint scan, making the cracking more difficult. Account lockout policies are essential and should be configured to lock an account after a certain number of unsuccessful login attempts, limiting the success of online attacks. Monitoring login attempts and detecting unusual activity such as brute-force attempts, is also necessary for detecting and stopping attacks quickly. Educating users about password security is crucial because users need to understand the importance of strong, unique passwords for different websites and not to reuse passwords.

In summary, successful password cracking attacks rely on weaknesses in how passwords are created, stored, and transmitted. Implementing a combination of complex passwords, secure hashing with salts, multi-factor authentication, account lockout policies, and user education greatly enhances password security and makes password cracking more difficult and costly for attackers.