How are password lists generated by attackers?

That's a very insightful question! Attackers generate password lists using a variety of methods and sources, often combining them to create highly effective lists. Here's a breakdown of how they do it:

1. Data Breaches and Leaks:

   • This is one of the most significant sources. When a website or service is hacked, user data, including usernames and passwords (often hashed or encrypted, but sometimes plain text), can be stolen. Attackers compile these leaked credentials into massive "combo lists."
   • These lists are frequently shared and traded on underground forums.

2. Publicly Available Wordlists/Dictionaries:

   • Attackers use freely available wordlists that contain common words, jargon, names, places, and popular culture references. These are often compiled by security researchers or white-hat hackers.
   • Examples include simple dictionary files in various languages, or more targeted lists like common sports terms, book titles, etc.

3. Password Pattern Generation (Rule-Based Attacks):

   • Many users create passwords by adding numbers or special characters to common words (e.g., password123, summer!).
   • Attackers use tools that apply known transformation rules to words from dictionaries or leaked passwords. These rules can include:
     • Appending numbers: password -> password1, password01, password123
     • Capitalizing letters: password -> Password, pAssword
     • Substituting characters (leetspeak): password -> p4ssw0rd, p@ssw0rd
     • Adding special characters: password -> password!, password@
     • Reversing words, repeating characters, etc.

4. Combinator Attacks:

   • This method combines smaller lists of passwords or words. For example, if an attacker has a list of common names and a list of common numbers, they might combine them to create John123, Mary456, etc.
   • Tools can also combine elements from different leaked password lists to create new, unique combinations.

5. Information Gathering (OSINT - Open Source Intelligence):

   • Attackers might gather personal information about a target from social media or public records (e.g., birth dates, pet names, family members, favorite sports teams).
   • This information is then used to generate highly personalized password guesses that are more likely to succeed against a specific individual.

6. "Crunch" or Password Generators:

   • There are specialized tools (like crunch in Kali Linux) that can generate custom wordlists based on specified character sets, minimum/maximum lengths, and other patterns. This is useful for more targeted brute-force attacks where the attacker has some idea of the password structure.

By leveraging these techniques, attackers can build incredibly large and diverse password lists that dramatically increase their chances of cracking accounts, especially those protected by weak or common passwords. That's why the step highlights the vulnerability of simple passwords like those in 500-worst-passwords.txt.