Hydra: Password Cracking and Security Testing in Kali Linux

Hydra: Password Cracking and Security Testing in Kali Linux

Password security is a paramount concern in the world of cybersecurity. Weak passwords are a common entry point for attackers seeking unauthorized access to systems. This article explores Hydra, a versatile password cracking tool used for security testing in Kali Linux. We will delve into its capabilities, installation, usage, attack modes, and best practices.

Table of content

1. Understanding Password Cracking

What is Password Cracking?

  • Password cracking is the process of attempting to guess or discover a password by exploiting vulnerabilities in the target system’s security.

Why is Password Cracking Important?

  • Password cracking helps identify weak passwords, vulnerabilities, and potential security risks in systems.
  • It assists in testing the effectiveness of security measures and aids in securing systems against unauthorized access.

2. What is Hydra?

What is Hydra Used For?

  • Hydra is a potent and flexible password cracking tool designed for security professionals and penetration testers.
  • It is used to test the strength of passwords, assess system security, and discover vulnerabilities related to weak passwords.

History of Hydra

  • Hydra, also known as THC-Hydra, was developed by THC (The Hacker’s Choice) as an open-source tool.
  • It has evolved over the years and gained popularity within the cybersecurity community for its effectiveness in password cracking.

3. Installing Hydra in Kali Linux


  • Hydra is pre-installed in Kali Linux, ensure you have a Kali Linux system set up and updated.

Install THC Hydra On Kali Linux

Hydra is pre-installed on Kali Linux and you will already have a new version of Hydra installed.

But if you wish to use other Debian based Linux Operating Systems, download from the repository by running the following command:

sudo apt-get install hydra

Also, you can download the latest version from THC’s public GitHub development repository. Open your terminal and run the commands below to downloadconfigurecompile, and install hydra:

git clone https://github.com/vanhauser-thc/thc-hydra.git
cd thc-hydra
make install

Install THC Hydra On Windows

The THC-HYDRA tool compiled for Windows

4. Basic Usage of Hydra

Running Hydra

Here’s a basic usage example of Hydra:

hydra -l username -P /path/to/passwords.txt ftp://targetIP

Hydra commands and variation

Hydra provides a range of command-line options to customize and control the password cracking process. Here are some commonly used command-line options and variations for Hydra:

Basic syntax:

   hydra [options] <target> <service> [options]


-l : Single username to target.
-L : Provide a file containing a list of usernames to target.
-p : Single password to test.
-P : Provide a file containing a list of passwords to test.
-e : Additional options for password generation (e.g., 'n' for a number, 's' for a symbol, 'r' for a reversed password).
-t : Set the number of parallel threads to use (default: 16).
-s : Specify a different port to use for the target service.
-f: Exit after the first successful login attempt.
-vV: Increase verbosity level (e.g., -v for verbose output, -V for very verbose output).
-o : Save the output to a file.

Service-specific options:

-s : Different port to use for non-standard services.
-S: Use SSL/TLS for the target service.
-x : Define a range for password length (e.g., -x 6:8:2 tests passwords of length 6, 8, and all values in between).
-C : Provide a file containing custom login attempts in a specific format for a particular service.

These are only a few of the alternatives accessible in Hydra. For a complete list of options and their usage, visit the Hydra documentation (man hydra in the terminal).

Remember that when undertaking security testing or penetration testing activities, it is critical to use Hydra responsibly and legally, securing necessary authorization and according to ethical norms.

5. Hydra Attack Modes

Hydra offers multiple attack modes to crack passwords effectively. Each mode has its unique approach and use cases.

Dictionary Attack

A Dictionary Attack is a method used by cyber attackers to systematically guess passwords. They use a predefined list, or “dictionary,” to test words or phrases, seeking unauthorized access. This relies on the assumption that users often choose easily guessed passwords. Attackers automate this process, testing each word against the target system. To defend against Dictionary Attacks, users must create strong, unique passwords, and systems should enforce security measures like account lockouts and monitoring for suspicious activity.

Brute Force Attack

A Brute Force Attack is an approach where attackers systematically try every possible combination of characters to discover a password. This method is comprehensive but can be time-consuming and resource-intensive. Strong passwords, account lockout policies, and rate limiting are used to defend against such attacks.

Brute Force vs. Dictionary Attack

Here’s a comparison of Brute Force and Dictionary Attacks in a table:

AspectBrute Force AttackDictionary Attack
MethodologyTries every possible combination of characters.Tries a predefined list of words or phrases.
EfficiencyThorough but time-consuming and resource-intensive.Faster but relies on user tendencies and common words.
Success RateHigh probability of success eventually.Success depends on the quality of the dictionary.
Suitable TargetsEffective when no information about the password.Effective when users choose easily guessable passwords.
Resource IntensityRequires significant computational power.Less resource-intensive compared to brute force.
DetectionMore likely to trigger intrusion detection systems.Less likely to trigger alarms due to fewer attempts.
MitigationStrong passwords, account lockouts, rate limiting.Strong, unique passwords, and account lockout policies.
comparison of Brute Force and Dictionary Attacks

These are the key differences between Brute Force and Dictionary Attacks, highlighting their respective strengths, weaknesses, and suitable use cases.

Hybrid Attack

A Hybrid Attack is a password cracking technique that merges a dictionary of potential passwords with systematic rule-based variations. It aims to crack passwords more efficiently than brute force by starting with a structured list and applying modifications. Success depends on the quality of the dictionary and rule set. Strong, unique passwords are the best defense.

Combining Dictionary and Brute Force

To combine elements of dictionary and brute force attacks for increased efficiency:

  1. Create a Dictionary: Compile a list of potential passwords, including common words and phrases.
  2. Define Rules: Specify rules for modifying dictionary entries, such as capitalization, numbers, and special characters.
  3. Choose a Tool: Select a password-cracking tool that supports hybrid attacks.
  4. Configure the Attack: Set up the tool to use the dictionary and apply the defined rules.
  5. Execute the Attack: Run the hybrid attack to systematically generate password variations.
  6. Monitor Progress: Keep track of the attack’s progress and any successful matches.
  7. Adjust and Refine: If needed, refine the dictionary and rules, and repeat the process.

A Hybrid Attack combines dictionary efficiency with rule-based versatility for password cracking, making it faster and more targeted. Success depends on the quality of the dictionary, rules, and the complexity of the target password. Strong passwords are essential for defense.

Password List Attack

A Password List Attack, sometimes referred to as a Credential Stuffing Attack, is a method employed by attackers to gain unauthorized access to accounts or systems by using a precompiled list of username-password pairs. Unlike brute force or dictionary attacks, which systematically generate password guesses, a Password List Attack relies on the assumption that individuals reuse passwords across multiple accounts or systems. Here’s how it typically works:

  1. Compilation of Password Lists: Attackers gather lists of username-password combinations from previous data breaches, leaked databases, or other sources on the internet. These lists may contain credentials from various online services.
  2. Target Selection: Attackers identify specific target accounts or systems they want to compromise, such as email accounts, social media profiles, or online banking.
  3. Automated Login Attempts: Using automated tools or scripts, attackers systematically attempt to log in to the target accounts by providing the username-password pairs from their compiled lists.
  4. Credential Reuse: The success of this attack depends on individuals reusing the same passwords across different services. If a username-password pair from the list matches the credentials for the target account, the attacker gains unauthorized access.
  5. Account Takeover: Once access is gained, the attacker may perform various malicious activities, such as stealing personal information, sending spam, or taking control of the account for further exploitation.

To defend against Password List Attacks:

  • Encourage users not to reuse passwords across multiple accounts.
  • Promote the use of strong, unique passwords for each online service.
  • Implement multi-factor authentication (MFA) wherever possible to add an extra layer of security.
  • Continuously monitor login attempts for suspicious activity and implement account lockout policies.
  • Educate users about the risks of password reuse and the importance of password managers for securely storing and generating complex passwords.

Creating Password Lists

To create custom password lists tailored to specific targets using the Crunch wordlist generator in Kali Linux:

  1. Define the Target Audience: Identify the specific user profiles or targets for which you need custom password lists.
  2. Install Crunch: If not already installed, install the Crunch wordlist generator on your Kali Linux system using the appropriate package manager.
  3. Gather Information: Collect information about the target audience, such as keywords, phrases, or patterns commonly associated with them.
  4. Generate Wordlists with Crunch: Use the Crunch tool to generate custom wordlists. Specify parameters like password length, character sets, and custom patterns relevant to the targets.
  5. Combine and Format: Merge the generated wordlists into a single file, ensuring proper formatting with one password per line.
  6. Test and Refine: Use the custom password list in your password-cracking or security testing tool. Analyze results and refine the list based on test outcomes.
  7. Maintain and Update: Keep the password lists dynamic and periodically update them to stay relevant as passwords change and new patterns emerge.

Creating tailored password lists with Crunch enhances the effectiveness of security testing, particularly when testing against passwords influenced by user roles, interests, or industry knowledge.

Using Common Password Lists

Using common password lists like “Rockyou.txt” and others can be an effective strategy in password cracking and security testing. These lists consist of frequently used passwords that have been compiled from various data breaches and sources. Here’s how you can utilize them:

6. Common Protocols and Services Targeted by Hydra


  • Detailed explanation of using Hydra for SSH password cracking.
  • Tips for securing SSH against Hydra attacks.


  • Using Hydra to crack FTP credentials.
  • Best practices for FTP server security.


  • Cracking passwords for web-based authentication using Hydra.
  • Recommendations for secure web applications.


  • Employing Hydra for Remote Desktop Protocol (RDP) password guessing.
  • Securing RDP access against brute force attacks.


  • Password cracking for MySQL databases with Hydra.
  • Database security measures to protect against attacks.


  • Utilizing Hydra to crack Telnet passwords.
  • Alternatives to Telnet for secure remote access.

7. How many possible protocols are there that can be cracked with Hydra?

Moreover, Hydra is a versatile tool that facilitates password cracking across a diverse array of protocols. The sheer number of protocols that Hydra can crack is extensive, and this list continues to expand as new protocols emerge. Some of the commonly supported protocols by Hydra include:

1. Network protocols:

  • FTP (File Transfer Protocol)
  • SSH (Secure Shell)
  • Telnet
  • SMTP (Simple Mail Transfer Protocol)
  • POP3 (Post Office Protocol version 3)
  • IMAP (Internet Message Access Protocol)
  • SMB (Server Message Block)
  • SNMP (Simple Network Management Protocol)
  • LDAP (Lightweight Directory Access Protocol)
  • RDP (Remote Desktop Protocol)
  • VNC (Virtual Network Computing)
  • MySQL
  • PostgreSQL
  • Oracle Listener

2. Web protocols:

  • HTTP (Basic and Digest Authentication)
  • Form-based authentication (POST requests)
  • HTTP-Proxy
  • HTTP-Proxy NTLM

3. Miscellaneous protocols:

  • Cisco AAA (Authentication, Authorization, and Accounting)
  • CVS (Concurrent Versions System)
  • IPMI (Intelligent Platform Management Interface)
  • NNTP (Network News Transfer Protocol)
  • PC-Anywhere
  • POP3S (POP3 over SSL)
  • Redis
  • Rexec (Remote Execution)
  • Rlogin (Remote Login)
  • Rsh (Remote Shell)
  • SIP (Session Initiation Protocol)
  • SMB (Server Message Block) over HTTP

Additionally, it is important to note that the aforementioned list is not exhaustive, and there may exist additional protocols that can be cracked using Hydra. These protocols may be supported through community contributions or custom modules.

8. Examples of Hydra Commands

Locate password list using this command

locate rockyou

1. For FTP Attack

hydra -l userlogin -P password-list-adress ftp://IP-Address -V

Example :

hydra -l msfadmin -P rockyou.txt -V

Note: in your case, your wordlist address and IP address can be different

2. For SSH Attack

Hydra -l userlogin -P password-list-adress ssh:// IP-Address -V

Example :

hydra -l msfadmin -P rockyou.txt ssh:// -V

Note: in your case, your wordlist address and IP address can be different

9. Best Practices for Using Hydra

  • Delve into the legal implications of using Hydra for password cracking.
  • Explore ethical considerations and responsible use of password cracking tools.

Obtaining Proper Authorization

  • The importance of obtaining explicit authorization before conducting security testing with Hydra.

Minimizing Impact on Target Systems

  • Tips for minimizing the potential impact of Hydra attacks on target systems.
  • Strategies for conducting tests without causing disruption.

Logging and Documentation

  • Importance of logging and documenting your Hydra testing procedures and results.

Legality of Using Hydra

It is crucial to bear in mind that using Hydra to crack passwords without proper authorization is both illegal and unethical. It is essential to always ensure that you possess appropriate permissions and strictly adhere to legal and ethical guidelines when employing such tools.

Ethical Considerations

Here are brief ethical guidelines for the responsible use of Hydra:

  • Obtain proper authorization.
  • Test only systems you own or have permission for.
  • Respect privacy and sensitive data.
  • Use legal password lists.
  • Monitor and limit testing impact.
  • Comply with laws and regulations.
  • Report vulnerabilities responsibly.
  • Educate and raise awareness.
  • Continuously improve skills and knowledge.
  • Document all testing activities.

Obtaining Permission and Authorization

11. Alternatives to Hydra

Here are brief alternatives to Hydra for password cracking and security testing:

  1. John the Ripper: Versatile and fast, supports various methods.
  2. Hashcat: Specializes in cracking password hashes.
  3. Medusa: For network-based attacks on various protocols.
  4. Cain and Abel: Windows-based, supports multiple attack methods.
  5. Aircrack-ng: Focuses on Wi-Fi security testing.
  6. THC-Hydra: Supports multiple network protocols.
  7. Patator: Versatile brute-forcing tool.
  8. Ophcrack: Recovers Windows passwords.
  9. RainbowCrack: Uses precomputed rainbow tables.
  10. Hybrid Attack Tools: Combine dictionary and brute force techniques.

Choose the tool that best suits your needs and always use them responsibly and legally.

12. Conclusion

In conclusion, Hydra is a powerful tool for security professionals and penetration testers. When used responsibly, ethically, and with proper authorization, it helps identify and mitigate security vulnerabilities related to weak passwords. Understanding its various attack modes and best practices is essential for effective security testing.


Certainly! Here are some frequently asked questions (FAQs) related to password cracking and security testing using tools like Hydra:

1. Is it legal to use password-cracking tools like Hydra for security testing?

Yes, it can be legal when used with proper authorization and within the scope of responsible security testing. Unauthorized or malicious use is illegal.

2. What are common password-cracking techniques used by tools like Hydra?

Common techniques include dictionary attacks, brute force attacks, hybrid attacks (combining dictionary and brute force), and rainbow table attacks.

3. How can I protect my systems from password-cracking attempts?

Implement strong password policies, employ multi-factor authentication (MFA), and monitor for suspicious login attempts. Regularly update passwords and educate users on password security.

4. What are rainbow tables, and how are they used in password cracking?

Rainbow tables are precomputed tables of possible password hashes. They can speed up password cracking by matching hashes to precomputed values.

5. Is it ethical to use leaked password lists in password cracking?

No, using stolen or leaked password lists is unethical and often illegal. Always use legal and ethical sources of password data.

6. How can I responsibly disclose vulnerabilities found during password cracking?

Report vulnerabilities to the system owner or responsible party in a responsible and coordinated manner. Avoid public disclosure until the issues are resolved.

7. Are there legal implications for password cracking without authorization?

Yes, unauthorized password cracking is illegal and can result in criminal charges and legal penalties.

8. What is the difference between a dictionary attack and a brute force attack?

A dictionary attack uses a list of common words and phrases to guess passwords, while a brute force attack systematically tries every possible combination of characters.

9. What are the advantages of using hybrid attacks over pure brute force or dictionary attacks?

Hybrid attacks combine the strengths of both approaches, making them more efficient and versatile. They save time by narrowing the search space while also exploring variations.

10. Can password-cracking tools like Hydra be used for legitimate security testing and audits?

Yes, password-cracking tools are valuable for testing the security of systems and identifying weak passwords, as long as they are used with proper authorization and ethical considerations.

Always use password-cracking tools responsibly, within legal boundaries, and with respect for privacy and security. Unauthorized or malicious use is strictly discouraged.

Hack Reveal


No comments yet. Why don’t you start the discussion?

Leave a Reply