Brute force attack

What is a brute force attack?

A brute force attack is a common cyber attack in which an attacker uses automated tools to try different combinations of passwords or keys until the right one is found. This method is based on “trial and error” and does not require complex techniques. The aim is to gain access to a system, account or database by systematically trying out all possible combinations of characters. The term “brute force” is derived from the fact that raw computing power is used to carry out the attack.

How does a brute force attack work?

A brute force attack uses programs that enter different password combinations quickly and automatically. These programs either systematically try all possible character combinations (alphanumeric, special characters, etc.) or use ready-made lists of frequently used passwords (dictionary attacks). If the attacker finds the right combination, he can compromise the system. The chances of success depend on the length and complexity of the password and the attacker’s computing power. Weak passwords with few characters or known patterns are particularly vulnerable.

What types of brute force attacks are there?

• • Simple brute force attacks: These attacks try every possible combination of characters (letters, numbers, symbols) until the correct password is found. This can be quick for simple passwords, but can take a considerable amount of time for more complex passwords.
  • Dictionary attacks: Attackers use ready-made lists of frequently used passwords. These lists contain common, easy-to-guess passwords such as “123456”, “password”, “qwerty” or similar combinations. Dictionary attacks are particularly effective against users who choose weak, frequently used passwords.
  • Hybrid attacks: This method combines a dictionary attack with a brute force attack. Frequently used passwords from the dictionary are used and supplemented with characters or numbers to test possible variants (e.g. “password1”, “passw0rd”).
  • Reverse brute force attacks: This technique involves trying a single password (or a list of common passwords) against many different usernames to gain access to different accounts.

How long does a brute force attack take?

The duration of a brute force attack depends on several factors: the complexity of the password, the available computing power and any protection mechanisms. Simple passwords such as “123456” can be cracked in seconds, while complex passwords with many characters, numbers and special characters can take months, years or even centuries, depending on their length. Modern tools use GPUs or even cloud services to dramatically increase the number of attempts per second, which means that even complex passwords can be cracked faster if no additional security precautions such as rate limiting are in place.

How can you protect yourself against brute force attacks?

• • Use strong passwords: A strong password should be at least 12 to 16 characters long and contain a combination of upper and lower case letters, numbers and special characters. It should not contain any easily guessable words, names or patterns.
  • Rate limiting: Systems should limit the number of possible login attempts per time unit. If too many failed attempts occur, the account can be blocked for a certain period of time or the attacker can be blocked.
  • Multi-factor authentication (MFA): MFA adds an additional layer of security by asking the user for a password and a second factor, such as a one-time code or biometric confirmation (e.g. fingerprint).
  • CAPTCHAs: The use of CAPTCHAs can prevent automated bots from passing through registration forms unhindered.
  • Password manager: Users should use a password manager to generate and store unique, complex passwords for each account.

Why are brute force attacks dangerous?

Brute force attacks pose a serious threat as they are often successful when users use weak passwords or when appropriate security measures have not been implemented. The attacker potentially gains full access to confidential data or systems, which can lead to data breaches, financial loss and reputational damage. Particularly problematic is that brute force attacks can go unnoticed as they are often carried out over long periods of time without the user or administrator realizing it.

How do you recognize a brute force attack?

A brute force attack can be recognized by various indicators:

• • High number of failed login attempts: A typical sign of a brute force attack is a large number of failed login attempts in a short period of time.
  • Unusual IP addresses: Attacks often come from IP addresses that do not match normal user activity or from geographic locations from which logins do not normally occur.
  • Increased server load: Since brute force attacks send many requests to the server, an increased load on servers or an overload of network resources can be an indication of an ongoing attack.
  • Unusual login activity: Multiple login attempts at unusual times of day or from different devices may indicate an attack.

What tools do attackers use for brute force attacks?

There are numerous tools that can be used for brute force attacks:

• • Hydra: A fast and flexible password cracking tool used for various protocols such as SSH, FTP and HTTP.
  • John the Ripper: A well-known open source tool for cracking passwords that combines brute force and dictionary attacks.
  • Hashcat: A powerful password cracking tool specifically designed to decrypt hash values using GPUs for increased speed.
  • Aircrack-ng: A tool that is mainly used for WLAN encryption attacks, but also uses brute force techniques to search for passwords.

Are brute force attacks different from other types of password attacks?

Yes, brute force attacks are based on a direct trial-and-error method, where the attacker has no prior knowledge of the password and tries all possible combinations. Other attack methods are often more sophisticated:

• • Phishing: Attackers deceive users into voluntarily disclosing their passwords by using fake websites or emails.
  • Social engineering: Attackers use interpersonal manipulation techniques to gain the victim’s trust and persuade them to disclose sensitive information.
  • Password sniffing: This involves intercepting network traffic in order to intercept unencrypted passwords.

What is the role of encryption in preventing brute force attacks?

Encryption plays a central role in protecting against brute force attacks, especially when it comes to storing passwords. Passwords should never be stored in plain text, but as hash values. A secure hash function (e.g. bcrypt, scrypt or Argon2) makes it extremely difficult for attackers to determine the original passwords, even if they capture the hashes. Salting should also be used – adding a random value to each password before it is hashed to reduce the effectiveness of dictionary or rainbow table attacks. Brute force attacks are a serious threat, but can be effectively mitigated by targeted security measures.

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