Dictionary Attacks

Cybersecurity Forensics Lesson 2.4.14

A dictionary attack is a form of password attack where the attacker uses a pre- determined list of passwords, or dictionary, to attempt to crack a password.

How to use

This kind of attacks is very similar to brute force attacking but instead uses more common passwords, making it faster and more likely to get a hit than running every single combination of letters. This can be done with “John the Ripper” tool that comes with most Kali distributions

How to Defend Against a Dictionary Attack

  • Do not use generic passwords or old passwords
    • Dictionary attacks use commonly-used passwords
    • Dictionary attacks often contain old passwords that make have been compromised in the past
  • Strong Passwords
  • Increasingly longer delay between failed attempts
  • Lockout after __ failed attempts
  • Two-Factor Authentication

Real Dictionaries

  • Real dictionary attacks use millions and billions of passwords.
  • The dictionary file sizes are enormous because of all the possible combinations they contain.
  • Where do these passwords come from?
    • When a cyber attack occurs, the culprits will sometimes leak usernames and passwords online. These are added into a continuously growing list of known passwords and circulated online.
  • A simple Google search will provide plenty of examples that can be