Holy Hash!

#security on software development security and web security, security best practices and discussions, break-ins and countermeasures. Everything you ever wanted to know about software security but were afraid to ask, for fear of not understanding the answer!

Common passwords blacklist

Any system that implements password authentication must check whether the passwords are not too common. Every system faces the brute-force attacks that try one or another list of most common password (and usually succeed, by the way). The system must have a capability to slow down an attacker by any means available: slowing down system response every time an unsuccessful authentication is detected, blocking an account for a short time after a number of unsuccessful authentication attempts or throwing up captchas.

Your password is not long enoughHowever, even the most sophisticated system fails if the user’s password is the most common word: “password”. The attacker simply succeeds then at once because that is likely to be the first word tried. So we need a system for blacklisting passwords that are thought of as most likely to be tried in a dictionary brute-force attack. This may be annoying for users of the system who may prefer to use a simple word as a password but this is the reality – any simple word used as a password is likely to be a security hole and must be banned.

While implementing the user login plugin for CakePHP I came across this simple question. Where do we get the password lists to check the newly entered passwords against? And here is a resource I can recommend: 62K Common Passwords by InfoSec Daily. Depending on your system’s speed you could use a smaller file of 6 MB, a 1.5 GB file that should take care of most common passwords or fuse the files into your own list.

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