There are several methods to crack passwords, with one being the use of a rainbow table. Despite its seemingly harmless name, a rainbow table attack is a serious cyber threat. Continue reading to learn what a rainbow table attack and how to defend against it.
What is a rainbow table attack?
A rainbow table attack is a type of cyberattack used to crack password hashes by leveraging a table of precomputed strings or commonly used passwords along with their corresponding hashes. This attack targets passwords that are hashed—secured through a hashing method—so let’s start by understanding hashing.
What is hashing?
Hashing is the process of converting a given key or string of characters (like a password or username) into a different string of characters (known as the hash value) to make it unreadable and unusable to cybercriminals. This is achieved by applying a one-way mathematical algorithm called a hash function. The hashed passwords are then stored on the company’s server.
By using hashing, a company doesn’t need to store actual passwords to authenticate users. When a user enters a password, it is converted into a hash value that is compared to the hash value stored on the server. If the values match, the user is authenticated and granted access. However, hashing algorithms can still be vulnerable to attacks like the rainbow table attack. So, how do these attacks work?
How does a rainbow table attack work?
Rainbow tables are created through chains of hashing and reduction operations. A hash function maps plaintexts to their hash values, while a reduction function maps hash values back to plaintexts.
The process involves four main steps:
- Generation: Start with a list of potential passwords and apply a hash function to each password to create a list of hashes. These hashes and their corresponding plaintext passwords are stored in the rainbow table.
- Reduction: Process the hashes using a reduction function to produce a new set of hashes. This function maps each hash to a new value, which is then used as the starting point for the next iteration. This step is repeated multiple times to build a chain of hashes.
- Lookup: To find corresponding plaintext passwords, a hacker uses the rainbow table to perform a reverse lookup. They start with the last hash in each chain and follow the chain backward until they find a match with the target hash.
- Cracking: When a match is found, the corresponding plaintext password is identified as the original password for the target hash. The hacker can then use this password to gain access to the account.
Rainbow tables require significant storage space, sometimes reaching terabytes, and can take a long time to generate. However, they are more efficient than brute-force or dictionary attacks because they avoid rehashing from scratch, using a precomputed hash database instead.
Dictionary attack vs. rainbow table attack
Both rainbow table attacks and dictionary attacks are methods hackers use to crack passwords.
| Attack Type | Description | Strengths | Weaknesses |
|---|---|---|---|
| Dictionary Attack | Uses a precompiled list of common passwords (dictionary) to compare against hashed passwords. | Effective against simple, commonly used passwords. Relies on the speed of the computer to try a large number of possible passwords. |
Less efficient with complex or uncommon passwords. Slower compared to rainbow table attacks. |
| Rainbow Table Attack | Uses a precomputed table of hashes to look up the plaintext version of a hashed password. | Requires less computing power and is faster than dictionary attacks. Quickly finds the plaintext password if it exists in the precomputed table. |
Takes longer to create the table. Requires significantly more storage space. |
Examples of rainbow table attacks
Hackers have several methods to gain unauthorized access to hashes and execute rainbow table attacks:
- Exploiting Weak Security: Hackers target companies or web applications with poor login data hashing techniques and weak overall security. Once they gain access to the database, they steal the stored hashes and use a rainbow table to crack them.
- Active Directory Vulnerabilities: Attackers exploit weaknesses in a company’s Active Directory to gain access to password hashes. Once they have the hashes, they can use a rainbow table attack to crack them.
- Phishing Attacks: Hackers can obtain users’ login details through phishing attacks. If the password hashes fall into the wrong hands and are not salted, there’s little that can be done to prevent them from being cracked.
How to prevent rainbow table attacks
You can prevent rainbow table attacks and protect your data through the following methods:
- Salting: The most effective defense against rainbow table attacks is salting. Salting involves adding random characters to the plaintext password before hashing it. This ensures that even identical passwords produce unique hashes, rendering rainbow table attacks ineffective.
- Use Secure Passwords: Choose unique, strong passwords and enable two-factor authentication (2FA) or biometric authentication whenever possible. Biometric passwords are immune to rainbow table attacks. Additionally, avoid weak or common passwords and refrain from reusing passwords across multiple accounts.
- Update Hashing Algorithms: Cybercriminals target servers and applications that use outdated password hashing algorithms. Ensure you are using the most current algorithms, and consider applying salting with a high salt value for added security.
- Server Protection: Secure your servers with the latest security software and regularly monitor them for any signs of attempted breaches.
FAQ’s
What is a rainbow table attack?
A rainbow table attack cracks password hashes using a precomputed table of hashes and their plaintext equivalents, allowing hackers to quickly find passwords.
How is a rainbow table attack different from a dictionary attack?
A dictionary attack compares hashed passwords to common passwords, while a rainbow table attack uses a precomputed hash table for faster results.
How do hackers perform a rainbow table attack?
Hackers steal password hashes and use a rainbow table to match them with plaintext passwords.
Why are rainbow tables effective?
Rainbow tables are efficient because they eliminate the need to rehash passwords, speeding up the cracking process.
How can I protect against rainbow table attacks?
Use salting, strong passwords, two-factor authentication, updated hashing algorithms, and secure servers to defend against rainbow table attacks.
Why is salting important?
Salting makes each password hash unique, preventing rainbow tables from effectively cracking the password.
Conclusion
Rainbow table attacks are a powerful and efficient method used by cybercriminals to crack password hashes, posing a significant threat to online security. However, by implementing strategies such as salting passwords, using strong and unique credentials, enabling two-factor authentication, and keeping your hashing algorithms and server security up to date, you can effectively protect your data and reduce the risk of falling victim to these attacks. Staying vigilant and proactive is key to maintaining robust cybersecurity.