When hackers plan an attack, they often engage in a numbers game. They can invest significant time pursing a single, high-value target—someone in the C-suite for example and do “spear phishing.” Or if they just need low-level access to gain a foothold in an organization or do reconnaissance, they target a huge volume of people and spend less time on each one which is called “password spray.” Last December Seema Kathuria and I described an example of the first approach in Spear phishing campaigns—they’re sharper than you think! Today, I want to talk about a high-volume tactic: password spray.
In a password spray attack, adversaries “spray” passwords at a large volume of usernames. When I talk to security professionals in the field, I often compare password spray to a brute force attack. Brute force is targeted. The hacker goes after specific users and cycles through as many passwords as possible using either a full dictionary or one that’s edited to common passwords. An even more targeted password guessing attack is when the hacker selects a person and conducts research to see if they can guess the user’s password—discovering family names through social media posts, for example. And then trying those variants against an account to gain access. Password spray is the opposite. Adversaries acquire a list of accounts and attempt to sign into all of them using a small subset of the most popular, or most likely, passwords. Until they get a hit. This blog describes the steps adversaries use to conduct these attacks and how you can reduce the risk to your organisation.
Three steps to a successful password spray attack:
Step 1: Acquire a list of usernames
Step 2: Spray passwords
Step 3: Gain access