18. August 2009 · Comments Off on Gmail vulnerability shows the value of strong (high entropy) passwords · Categories: Authentication, Malware, Risk Management, Security Management, Security Policy · Tags: , , , , , , , , ,

Weak passwords and other password issues continue to be the bane of every security manager's existence. Becky Waring from Windows Secrets reports on a Gmail vulnerability where an attacker can repeatedly guess your password using Gmail's, "Check for mail using POP3"
capability. This is a service Gmail provides that enables you to use an email client rather than the Gmail browser interface. You can read the details of the vulnerability at Full Disclosure.

The unfortunate reality is that we have reached a point in the evolution of technology that if an attacker is in a position to implement an unimpeded repetitive "guessing" attack on your password, like this Gmail vulnerability, there is no password you can remember that can survive the attack. In other words, if you can remember the password, it's too weak, and it will be cracked.

NIST Special Publication 800-63 rev1 "Electronic Authentication Guideline" Appendix A (Page 86) discusses the concepts of password strength (entropy) in detail.

The only way you can really protect yourself is by using an automated password manager. LifeHacker has a very good review of the top choices available.One of the side benefits of these products, is that you should not have to physically type your passwords, thus reducing the risk associated with keyloggers, which I discussed in previous posts here and here.

Steve Gibson has a site called Perfect Passwords that automatically generates high entropy passwords.

At the very least, follow the advice in Becky Waring's column.