How to prevent the harm of Rainbow Table Attacks?

Brady Yonng

Sep 8, 2023 | 7 min read

Online threats

Overview

Rainbow table attacks are a common password cracking technique that takes advantage of precomputed tables of hash values and their corresponding plaintext passwords to quickly discover a user's password. This method can be highly effective against users who use weak passwords or hash functions without salting. This article will explain what a rainbow table attack is, how it works, provide some examples, and discuss methods of defense.

What is a Rainbow Table Attack?

How Does a Rainbow Table Attack Work?

Examples of Rainbow Table Attacks

How to Defend Against Rainbow Table Attacks?

Using MetroVPN for Online Threats

What is a Rainbow Table Attack?

A rainbow table attack is a password cracking technique based on time-space trade-offs. It works by precomputing a range of hash values and their corresponding plaintext passwords, storing them in a data structure known as a rainbow table. When an attacker obtains a hash value, they can look up if there's a matching plaintext password in the rainbow table, revealing the user's password.

How Does a Rainbow Table Attack Work?

The specific steps of a rainbow table attack are as follows:

① Generation

Rainbow tables start by listing potential passwords and applying a hash function to each password, generating a list of hashes. The resulting hash values and their corresponding plaintext passwords are stored in the rainbow table.

② Reduction

The hash values in the rainbow table are further processed using a reduction function to generate a new set of hashes. The reduction function maps each hash to a new value, and these new values serve as the starting point for the next step. This step is repeated multiple times, creating a chain of hashes.

③ Lookup

When an attacker obtains a hash value, they can use the rainbow table to find the corresponding plaintext password. They reverse-lookup the hash values in the rainbow table, starting from the last hash value in each chain and working backward until they find a matching hash value.

④ Cracking

Once a corresponding hash value is found, it means the plaintext password associated with the target hash value has been discovered. The attacker can now use it for unauthorized access, such as logging into another person's account.

Examples of Rainbow Table Attacks

Rainbow table attacks can be used to crack various types of passwords, including Windows NTLM, Unix crypt, WPA-PSK, and more. Here are some real-world examples:

① In 2007, a German hacker used a rainbow table attack to crack the passwords of 1.5 million users in the Turkish Citizenship Database and made them public online.

② In 2010, a French hacker used a rainbow table attack to crack the passwords of 1.88 million users on the Gawker Media website and published them online.

③ In 2012, a Russian hacker used a rainbow table attack to crack the passwords of 6.4 million users on the LinkedIn website and made them public online.

How to Defend Against Rainbow Table Attacks?

While rainbow table attacks can be powerful, they are not undefeatable. Here are some common defense methods:

① Use Strong Passwords

Strong passwords are lengthy and include a combination of numbers, letters, and special characters. They are less susceptible to guessing and rainbow table attacks.

② Use Salted Hash Functions

Salted hash functions involve adding a random string (called a salt) to the original value before hashing it. This adds complexity to hash values, making it impractical to look them up in a precomputed rainbow table.

③ Use Slow Hash Functions

Slow hash functions, such as bcrypt, scrypt, or PBKDF2, are deliberately designed to be computationally intensive. They increase the time and resources required for generating and searching rainbow tables.

④ Regularly Update Passwords

Encourage users to regularly update their passwords to minimize the risk of rainbow table attacks against older or compromised passwords.

Using MetroVPN for Online Threats

In addition to defending against rainbow table attacks, there are many other online threats, such as network surveillance, identity theft, and malware. To protect yourself from these threats, we recommend using MetroVPN to safeguard your online security and privacy.

MetroVPN is an excellent VPN service provider that offers the following advantages: