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What Is a Brute-Force Attack? How It Works and How to Defend Against It

Tap each term to understand brute-force attacks and how to defend against them.

What a brute-force attack is

A brute-force attack systematically tries every possible password combination, one after another, until it finds the correct one, carried out by automated software capable of attempting an enormous number of combinations in a short time, not a person typing by hand.

Dictionary attacks: a common variation

Rather than trying every possible combination blindly, a dictionary attack prioritizes commonly used passwords and real words first, meaning short, simple passwords are cracked much faster.

Account lockout policies

Many services temporarily lock an account or require additional verification after a certain number of failed login attempts in a short window, making sustained brute-force attempts much harder to carry out.

How CAPTCHA filters out automated attempts

The CAPTCHA challenges you see on login or sign-up screens exist specifically to distinguish a human from automated software, which helps block the kind of repeated automated attempts a brute-force attack depends on.

Using a long, unpredictable password or passphrase

The more possible combinations there are, the longer a brute-force attack takes to succeed, so a long password unrelated to your personal information, or a passphrase built from unrelated words, is one of the most effective defenses.

Rate limiting on the service side

Service operators often throttle or block an unusually high volume of login requests coming from the same IP address or account in a short time. You can't configure this yourself, but it's a security factor worth considering when choosing which services to trust.

Why a longer password matters more than you'd think

As the number of possible characters and the length of a password increase, the number of possible combinations grows exponentially. That means the time required to crack it through brute force grows dramatically too, so a longer, harder-to-predict password beats a short one by a wide margin.

Two-factor authentication adds real backup

Even if a password does get cracked, having two-factor authentication (2FA) enabled means there's a second checkpoint standing between an attacker and your account, so it's worth pairing both defenses together.

Frequently Asked Questions

Does mixing in special characters make a password automatically safe?

Mixing in special characters does increase the number of possible combinations and helps, but a short password can still be vulnerable regardless. Increasing overall length is often more effective than just adding character variety.

I got an alert that my account was locked after several failed login attempts, was I attacked?

It could simply be a mistyped password on your end, but if the alert mentions repeated unfamiliar attempts, it may indicate you were targeted by a brute-force attempt. Changing your password and enabling two-factor authentication is a safe response either way.