Brute Force Attacks: How Hackers Gain Unauthorized Access

Cybersecurity plays an essential role in today’s interconnected digital world. Malicious agents’ techniques for breaking into systems and damaging confidential information are changing along with technology. The brute force attack is one such technique that is still widely used. In this blog, we’ll delve into what brute force attacks are, explore their various types, and discuss effective countermeasures to safeguard against them.

Brute Force Attacks

These types of attacks tend to target at password-protected accounts. To obtain unauthorized access to a user’s account, the attacker uses software that generates a series of successive attempts. Simple, short passwords are particularly vulnerable to brute force assaults if they are not shielded by other security measures like account lockout policies that expire after a set number of unsuccessful tries or CAPTCHAs, which prevent automated submissions. However, since the number of possible combinations that the attacker’s software must evaluate grows rapidly, brute force attacks become more difficult as password complexity increases. 

Types of Brute Force Attacks

Simple Brute Force

This is the simplest version, in which the attacker manually attempts to guess the password by entering different letter, number, and symbol combinations. It is time-consuming and inefficient, but surprisingly effective against weak, predictable passwords like “123456” or “password123”.

Dictionary Attacks

Dictionary attacks use pre-made lists of frequently used words, phrases, variations, and compromised passwords in place of random guesses. These lists can be quite long and modified based on the activities or background of the person who will be receiving them. Dictionary attacks are far quicker and more effective than simple brute force, particularly when used against users who repeat passwords for many accounts.

Hybrid Brute Force

This combines dictionary attacks with the brute-force method. It starts with a smaller list of common passwords and then expands it with character substitutions, variations, and dictionary entries. This increases the attack’s target while maintaining its focus on popular password combinations.

Reverse Brute Force

In this case, the attacker is already aware of certain details about the password, such as its length or the characters that have been used. Based on this information, they then create targeted lists, which significantly decrease the number of possibilities and boost the attack’s speed and success rate.

Credential Stuffing

This involves attempting various username and password pairs that have been compromised or released through data breaches on several platforms. Attackers take advantage of the fact that a lot of people share login credentials between accounts. Automated credential stuffing is very successful, especially when used against platforms with weak login security.

Rainbow Table Attacks

These attacks use pre-computed hashes of common passwords and then compare them to the hashed password of the target system. A successful match discovers the matching password in the rainbow table without revealing the password itself. Although creating and storing the rainbow tables takes a lot of resources, this can be faster than brute-forcing the password itself.

Password Spraying

Password spraying relies on a single, common password against a large number of accounts, as compared to targeting each account individually. This aims to exploit weak password policies or password reuse across different platforms. While less targeted, it can effectively identify vulnerable accounts and gain access to multiple systems at once.

Brute Force Attacks on RDP Connections

One prominent method for remote computer access is Remote Desktop Protocol, or RDP. Brute force tactics can be used by attackers to guess RDP login credentials and obtain access to the remote system without permission. This might serve as an entry point to further attacks on the system’s data or network.

Tips To Prevent Brute Force Attacks

• Strong Password Policies: Enforce complex passwords that include a mix of uppercase and lowercase letters, numbers, and special characters. This exponentially increases the number of possible permutations a brute force attack would need to try.

• Account Lockout Mechanisms: Set up account lockouts after a certain number of failed login attempts. This stops continuous password guessing dead in its tracks but should be implemented thoughtfully to prevent denial of service situations through account lockout abuse.

• Two-Factor Authentication (2FA): Adding an additional layer of security beyond just a password significantly diminishes the effectiveness of brute force attacks, as the attacker also needs the second factor—usually a temporary code sent to a mobile device or generated by an authenticator app.

• CAPTCHA: Implement CAPTCHAs to challenge and block automated login attempts, ensuring that only humans can proceed with login attempts.

• Use of Security Software: Deploy security solutions that detect and block repeated failed login attempts, which are indicative of brute force attacks.

• Monitoring and Alerting: Monitor systems for unusual login activity and set up alerts for multiple failed login attempts.

• Network-Level Security: Utilize network security tools like firewalls and intrusion prevention systems to block traffic from IP addresses that are known sources of attacks.

• Educate Users: Regularly educate users about the importance of using strong passwords and the risks associated with weak authentication practices.

• Password Managers: Encourage the use of password managers to help users maintain unique, complex passwords for different sites and services, reducing the temptation to reuse passwords.

• VPN and Encrypted Connections: Use VPNs and ensure connections are encrypted to prevent attackers from intercepting credentials that could be used in brute force attacks.

• Banning IP Addresses: Implement rules to ban IP addresses that show signs of brute force attack behavior over a defined period.