What defines a rainbow attack?

A rainbow attack involves using precomputed tables of hash values, known as rainbow tables, to reverse the process of hashing and discover the original passwords. This method leverages the fact that many users create weak or common passwords, allowing attackers to efficiently find the plaintext password corresponding to a given hash.

In a rainbow attack, the attacker does not need to brute-force the password or attempt to guess it character by character. Instead, the attacker can look up the hash in the precomputed table, which saves a significant amount of time and computational resources compared to generating the hash from potential passwords on the fly.

This approach is particularly effective against systems that store passwords using weak hashing algorithms or no salt, since these conditions make it easier for attackers to match hash values from a rainbow table to actual passwords. Thus, the essence of a rainbow attack is in its targeted exploitation of hash functions combined with common password use to retrieve original passwords from their hashes.