Crack Linux MD5 Password Hash and Secure Your System

Now we can start using hashcat with the rockyou wordlist to crack the MD5 hashes. The rockyou wordlist comes pre-installed with Kali. If you are not using Kali you can use another wordlist, or download it from here.

CrackStation uses massive pre-computed lookup tables to crack password hashes.These tables store a mapping between the hash of a password, and the correctpassword for that hash. The hash values are indexed so that it is possible toquickly search the database for a given hash. If the hash is present in thedatabase, the password can be recovered in a fraction of a second. This onlyworks for "unsalted" hashes. For information on password hashing systems thatare not vulnerable to pre-computed lookup tables, see our hashing security page.

crack linux md5 password hash

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Crackstation's lookup tables were created by extracting every word from theWikipedia databases and adding with every password list we could find. We alsoapplied intelligent word mangling (brute force hybrid) to our wordlists to makethem much more effective. For MD5 and SHA1 hashes, we have a 190GB,15-billion-entry lookup table, and for other hashes, we have a 19GB1.5-billion-entry lookup table.

Are you a beginner in the domain of cybersecurity? Do you want to be on its offensive side? As a red teamer, you learn many techniques and tactics that help you perform the cyber kill chain activities. One such task is privilege escalation, where you get hold of password hashes.

hashcat is a powerful and versatile tool that brute forces the stored credentials using known hashes by conducting various modes of attacks. The article covers this password cracking utility used by penetration testers, system administrators, spies, or hackers to find passwords.

hashcat offers a variety of attack modes (Combinator, Rule-based, Brute-force guessing, hybrid, and dictionary attacks) to provide better coverage. Here is an explanation of some attacks that hashcat uses to crack hashed passwords:

Hence, if you come across a readable /etc/shadow file through any regular user account, you can get the hash value of the root account and crack the password hash using the hashcat utility.

Now use the hashcat utility to crack the hash with the -a flag for attack mode, -m flag for hash reference value (as it does not support hash function name), hash.txt file path, and a path to the wordlist rockyou.txt.

A well-built authentication system does not store user passwords in plain text and clear sight as they can cause security vulnerabilities. A better authentication mechanism stores passwords as hashes in secure and inaccessible files. However, a password cracker such as hashcat is designed to decipher or guess the passwords using various attack modes.

This article details ways a penetration tester must know to crack hashed passwords using the hashcat utility. As a red teamer, it's necessary to understand the techniques an attacker can use to compromise the authentication controls and provide guidelines on covering system loopholes.

In the SQL injection lesson, we were able to output MD5-hashed passwords from the database. I then proceeded to use an online website to crack a couple of the hashes in order to see the plaintext password. I also mentioned we could use tools in Kali to do this instead of the website.

After gaining access to a root account, the next order of business is using that power to do something more significant. If the user passwords on the system can be obtained and cracked, an attacker can use them to pivot to other machines if the login is the same across systems. There are two tried-and-true password cracking tools that can accomplish this: John the Ripper and Hashcat.

John the Ripper is a popular password cracking tool that supports many common hash types as well as a useful autodetect feature. It has been around for a while now, and as such, it continues to be one of the strongest and easiest to use crackers available.

Before we can feed the hashes we obtained into John, we need to use a utility called unshadow to combine the passwd and shadow files into a format that John can read. Run the following command to merge the data into a new text file called passwords.txt.

We can see that John detects the type of hash used as md5crypt, also known as aix-smd5, and after a bit of time, it completes the session successfully. Now we can use the --show flag to display the cracked passwords that John successfully recovered:

After the username in the first field, we can now see the cleartext password in the second field. It tells us that six out of seven password hashes were cracked; Depending on the hardware being used, the wordlist that's supplied, and the length and complexity of the passwords, various levels of success will be achieved.

The next tool that we will look at is Hashcat. This is an extremely powerful hash-cracking tool with a ton of features and both CPU-based and GPU-based versions available. As of Hashcat v3.00, the CPU and GPU tools were merged, with the CPU-only version becoming Hashcat-legacy.

The prevalence of cloud technologies and distributed computing brings a whole new angle to password cracking. Most of the time, hackers are running a virtual machine, laptop, or at best, a powerful desktop computer, but many online services utilize dedicated servers and resources for cracking hashes. Sites such as CrackStation, Online Hash Crack, and MD5/Sha1 Hash Cracker offer the convenience of password cracking right from the browser. None of these seemed to support the md5crypt hashes that we had, but it's easy to find support for many common hash formats such as MD5, SHA1, and LM.

One last quick note: If you can't find the right hash format online, or even if you just want to possibly save some time, it certainly doesn't hurt to consult Google. Sometimes if you just search for the exact hash you are trying to crack, you can get results. Chances are if it's a default or common password, or if it's a hash that's been cracked before, you can find it in the search results. A quick Google search could end up saving you a lot of time and effort.

In this series, we learned how to use Metasploit to compromise a web server and get a low-level shell, used a kernel exploit to perform local privilege escalation and gain root-level access, and cracked some password hashes using John the Ripper and Hashcat. A lot of times, a system can be owned using this exact same process, only with different exploits and attack vectors. Now that you have some more tools and techniques under your belts, get out there and practice away. Happy hacking!

Although the hashing algorithms cannot be reversed, password hashes could be cracked. Hackerscan generate hashes from a dictionary of strings that are commonly used as passwords. If hackersgain access to a database of hashed passwords, they can calculate the hash code for each string inthe database and match it with the current hash code. If one in the database matches, the plaintextpassword of that hash is known. This is so-called brute force dictionary attack.

John the Ripper is one of the well-known fast password cracking tool that can crack passwordsthrough a dictionary attack or through the use of brute force. It can be downloaded free atwww.openwall.com/john/.

Hashcat supports five unique modes of attack for over 300 highly-optimizedhashing algorithms. hashcat currently supports CPUs, GPUs, and otherhardware accelerators on Linux, and has facilities to help enabledistributed password cracking.

Hashcat is a popular password cracker and designed to break even the most complex passwords representation. To do this, it enables the cracking of a specific password in multiple ways, combined with versatility and speed.

Hashcat turns readable data into a garbled state (this is a random string of fixed-length size). Hashes do not allow someone to decrypt data with a specific key, as standard encryption protocols allow. Hashcat uses precomputed dictionaries, rainbow tables and even brute-force approaches to find an effective and efficient way to crack passwords.

The simplest way to crack a hash is to try first to guess the password. Each attempt is hashed and then is compared to the actual hashed value to see if they are the same, but the process can take a long time.

dc647eb65e6711e155375218212b3964:Passwordeb61eead90e3b899c6bcbe27ac581660:HELLO75b71aa6842e450f12aca00fdf54c51d:P455w0rd2c9341ca4cf3d87b9e4eb905d6a3ec45:Test1234958152288f2d2303ae045cffc43a02cd:MYSECRETThese passwords are weak, and it does not take much effort or time to crack them. It is important to note that the simpler the password is, the easier it will be to detect.

Additionally, there are some GUI that makes hashcat easy to use. Hashview is one of the projects. This is a tool for security professionals to help organize and automate the repetitious tasks related to password cracking. In detail, it is a web application that manages Hashcat commands.

In this article, I would like to highlight the importance of using complex passwords when hashed with the MD5 128-bit algorithm. I will demonstrate the cracking of MD5 salted passwords using Kali Linux and a password cracking tool, John the Ripper.

Cisco IOS devices use the MD5 algorithm to hash username passwords created by administrators. When weak password strings are used that are protected with MD5 they become susceptible to attacks. MD5 passwords use something called salted hash, this is a four-character phrase that is generated and combined with the password.

Extracts of the following demonstration are taken from a CCNA Security lab I have been working on. It was such an informative lab, I decided to document it and share it with the SYNACK community. To carry out MD5 cracking we will use John the Ripper to crack a weak hashed password and then we will use a custom dictionary to carry out the second attack. 2ff7e9595c