Brute-force attacks remain one of the simplest yet most effective techniques used by cybercriminals today.
Attackers continue to exploit weak passwords, reused credentials, and poorly protected login systems.
Understanding what a brute-force attack is and how to stop one is essential for any organisation looking to reduce the likelihood of a data breach or cyber attack.
This guide explains what a brute-force attack is, how it works, which businesses should be aware of it, and what you can do to make these attacks far more difficult for cybercriminals.
What is a brute-force attack?
A brute-force attack is a method used by cybercriminals to gain access to an account or system by trying every possible combination until they find the correct one.
Brute-force attacks are trial and error.
When passwords are weak or if they have been reused across multiple accounts, attackers can break in very quickly.
Because the technique is straightforward, brute-force attacks are common across a wide range of cyber incidents.
How brute-force attacks work
Brute-force attacks typically fall into two categories: online and offline attacks. They share the same goal but work very differently.
Online brute-force attacks
Online brute-force attacks occur when cybercriminals try to guess a password or log in to a live website or system.
These are slower due to factors such as network lag and the security measures an organisation has in place, such as limiting the number of tries, locking accounts after a couple of failed attempts, or requiring CAPTCHA.
Because they try so many times, these attacks are usually much easier to spot as they create a lot of failed login alerts.
Offline brute-force attacks
Offline brute-force attacks are when cybercriminals get hold of a database of scrambled passwords (hashes), usually from a data breach or a badly set-up system.
Since they’re doing the cracking on their own computers, they don’t have to worry about getting locked out.
A mix of modern cracking tools and powerful technical specs on a cybercriminal’s computer means that they can try billions of passwords per second. This makes it very easy to break short or weak passwords.
These offline attacks are much more dangerous and are often the method behind huge data breaches of login details.
Types of brute-force attacks
Bru-force attacks take many forms.
While the underlying principle remains the same, the way they’re carried out depends on what cybercriminals are after and the weak spots they can exploit.
Pure brute force
This type of attack involves trying every possible character combination in sequence. Although it eventually works, it is much slower and easier to detect.
Dictionary attack
A dictionary attack uses lists of common words or predictable passwords.
This becomes a problem when people still use incredibly common and weak passwords, such as “password” or “123456”, making this method faster and more successful.
Hybrid attacks
Hybrid attacks combine dictionary words with predictable variations, such as turning “Password” into “Password1!”.
They exploit common patterns in human-created passwords.
Password spraying
Password spraying tests a small number of common passwords across many accounts, helping attackers avoid triggering lockouts.
It often targets organisations with large user bases as it increases their chances of getting in.
Credential stuffing
Credential stuffing uses usernames and passwords stolen from other breached sites to try to log into different systems.
Because password reuse is widespread, credential stuffing remains a significant risk.
Offline cracking
As mentioned above, offline brute-force attacks allow attackers to run password-guessing attempts locally on powerful hardware.
No alerts or lockouts make this technique particularly dangerous.
To reduce the potential damage from these types of attacks, lockouts after failed login attempts and 2FA are crucial.
What is the purpose of brute-force attacks?
Steal personal information
Cybercriminals use brute-force attacks to get into accounts that hold valuable personal data. Once inside, they may access names, addresses, dates of birth, or financial details.
Stolen information can then be sold on the dark web, used to commit identity fraud, or leveraged to break into other accounts belonging to the same victim.
Because many people reuse passwords, one successful attack can lead to a chain of compromised systems.
Spread malware
Gaining access to an account or system through brute force is often just the starting point. Once in, attackers may install malware such as keyloggers, ransomware, or remote access tools.
These can allow them to spy on activity, steal more information, or lock an organisation out of its own systems.
Hijack organisational systems
In many cases, the goal is not just to steal data but to take control of internal systems. This could involve accessing admin panels, cloud environments, email servers, or financial data.
Once attackers have this level of access, they can manipulate settings, create new accounts, divert payments, or shut down services.
For organisations, this can lead to big financial losses and costly repairs to get systems back up and running to their normal state.
Ruin or damage a company or organisation’s reputation
A successful brute-force attack can have long-term consequences on an organisation’s reputation. Customers lose trust when they hear about breaches, especially if the data is sensitive.
How to prevent brute-force attacks
Preventing brute-force attacks requires a combination of secure password practices, strong technical controls, and proactive monitoring.
Strong, unique passwords remain the key aspect of protection. Longer passwords or passphrases significantly increase your defence towards brute-force attempts.
Two-factor authentication (2FA) is one of the most effective defences, preventing attackers from logging in even if they guess the correct password.
Challenge-response tools such as CAPTCHAs help block automated bots, particularly on exposed login pages.
Rate limiting and account lockouts prevent repeated login attempts and make sustained brute-force attempts considerably more difficult.
Continuous monitoring for unusual behaviour, such as multiple failed logins across different accounts or logins from unfamiliar locations, provides important early warnings, especially against distributed attacks.
Remember, secure password storage is essential.
Using modern algorithms in your password systems ensures that even if attackers do manage to get hold of password databases, cracking attempts are significantly delayed or blocked altogether.
A final thought
Brute-force attacks only succeed when security controls allow them to.
When businesses use stronger passwords, enforce multi-factor authentication (MFA), secure their authentication systems, and proactively monitor for suspicious activity, brute-force attempts quickly become inefficient and costly for attackers. Small improvements in passwords and security defences can make the difference between preventing an attack and becoming the next breach headline.
