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Password Security Concepts

Introduction

Passwords are the most widely used form of authentication throughout the world. A username and password are used for logging in your social media accounts, banks, etc.

Password cracking is the process of recovering passwords from data that have been stored in or transmitted by a computer system. A common approach is to try guesses for the password and check them against an available cryptographic has of the password. This process is often called as the brute-force attack.

In general, passwords are not stored in clear text. In fact, passwords are stored as hashes. Hashes or hash values are the values returned by a function, called as the hash-function, which is used to map data of arbitrary size to data of fixed size.

Types of attacks

Dictionary Attacks

A dictionary attack is the simplest and fastest password cracking attack. The implementation of the attack simply runs through a dictionary of words trying each one of them to see if they work. This attack is possible because the computers now-a-days have performance capabilities. This is usually the first approaching for password cracking.

Rainbow Table Attacks

Mostly, passwords are not stored in plaintext. They are mostly stored in the form of a hash. Hence, even if the attacker dumps the passwords, all he gets is the hash value of the password, which cannot be used to authenticate. One way to crack this encryption is to take the dictionary file, hash each word and compare it to the hashed password. But this is very time consuming. A faster approach would be to take a table with all the words in the dictionary already hashed and compare this hash with the found password hash. This type of attack is called Rainbow Table Attack.

Brute-Force Attacks

This type of attack is the most type consuming approach. This should be your last resort to crack the password. Brute-force attack techniques tries to attempt all the possibilities of all the letters, numbers and special characters that can be combined to generate a password. Hence, this technique requires a lot of computing power.

Popular Password Cracking Tools


1. Hashcat

Hashcat is one of the most popular and widely used password crackers in existence. It is available on every operating system and supports over 300 different types of hashes.

Hashcat enables highly-parallelized password cracking with the ability to crack multiple different passwords on multiple different devices at the same time and the ability to support a distributed hash-cracking system via overlays. Cracking is optimized with integrated performance tuning and temperature monitoring.

2. John the Ripper

John the Ripper is a well-known free open-source password cracking tool for Linux, Unix and Mac OS X. A Windows version is also available. 

John the Ripper offers password cracking for a variety of different password types. It goes beyond OS passwords to include common web apps (like WordPress), compressed archives, document files (Microsoft Office files, PDFs and so on), and more.

A pro version of the tool is also available, which offers better features and native packages for target operating systems. You can also download Openwall GNU/*/Linux that comes with John the Ripper.

3. Brutus

Brutus is one of the most popular remote online password-cracking tools. It claims to be the fastest and most flexible password cracking tool. This tool is free and is only available for Windows systems. It was released back in October 2000.

Brutus supports a number of different authentication types, including:

HTTP (basic authentication)
HTTP (HTML Form/CGI)
POP3
FTP
SMB
Telnet
IMAP
NNTP
NetBus
Custom protocols
It is also capable of supporting multi-stage authentication protocols and can attack up to sixty different targets in parallel. It also offers the ability to pause, resume and import an attack.

Brutus has not been updated for several years. However, its support for a wide variety of authentication protocols and ability to add custom modules make it a popular tool for online password cracking attacks.

4. Wfuzz

Wfuzz is a web application password-cracking tool like Brutus that tries to crack passwords via a brute-force guessing attack. It can also be used to find hidden resources like directories, servlets and scripts. Wfuzz can also identify injection vulnerabilities within an application such as SQL injection, XSS injection and LDAP injection.

Key features of the Wfuzz password-cracking tool include:

Injection at multiple points in multiple directories
Output in colored HTML
Post, headers and authentication data brute-forcing
Proxy and SOCK support, multiple proxy support
Multi-threading
HTTP password brute-force via GET or POST requests
Time delay between requests
Cookie fuzzing


5. THC Hydra

THC Hydra is an online password-cracking tool that attempts to determine user credentials via brute-force password guessing attack. It is available for Windows, Linux, Free BSD, Solaris and OS X.

THC Hydra is extensible with the ability to easily install new modules. It also supports a number of network protocols, including Asterisk, AFP, Cisco AAA, Cisco auth, Cisco enable, CVS, Firebird, FTP, HTTP-FORM-GET, HTTP-FORM-POST, HTTP-GET, HTTP-HEAD, HTTP-PROXY, HTTPS-FORM-GET, HTTPS-FORM-POST, HTTPS-GET, HTTPS-HEAD, HTTP-Proxy, ICQ, IMAP, IRC, LDAP, MS-SQL, MYSQL, NCP, NNTP, Oracle Listener, Oracle SID, Oracle, PC-Anywhere, PCNFS, POP3, POSTGRES, RDP, Rexec, Rlogin, Rsh, SAP/R3, SIP, SMB, SMTP, SMTP Enum, SNMP, SOCKS5, SSH (v1 and v2), Subversion, Teamspeak (TS2), Telnet, VMware-Auth, VNC and XMPP.

6. Medusa

Medusa is an online password-cracking tool similar to THC Hydra. It claims to be a speedy parallel, modular and login brute-forcing tool. It supports HTTP, FTP, CVS, AFP, IMAP, MS SQL, MYSQL, NCP, NNTP, POP3, PostgreSQL, pcAnywhere, rlogin, SMB, rsh, SMTP, SNMP, SSH, SVN, VNC, VmAuthd and Telnet.

Medusa is a command-line tool, so some level of command-line knowledge is necessary to use it. Password-cracking speed depends on network connectivity. On a local system, it can test 2,000 passwords per minute.

Medusa also supports parallelized attacks. In addition to a wordlist of passwords to try, it is also possible to define a list of usernames or email addresses to test during an attack.

7. RainbowCrack

All password-cracking is subject to a time-memory tradeoff. If an attacker has precomputed a table of password/hash pairs and stored them as a “rainbow table,” then the password-cracking process is simplified to a table lookup. This threat is why passwords are now salted: adding a unique, random value to every password before hashing it means that the number of rainbow tables required is much larger.

RainbowCrack is a password cracking tool designed to work using rainbow tables. It is possible to generate custom rainbow tables or take advantage of preexisting ones downloaded from the internet. RainbowCrack offers free downloads of rainbow tables for the LANMAN, NTLM, MD5 and SHA1 password systems.

This tool is available for both Windows and Linux systems.

8. OphCrack

OphCrack is a free rainbow table-based password cracking tool for Windows. It is the most popular Windows password cracking tool but can also be used on Linux and Mac systems. It cracks LM and NTLM hashes. For cracking Windows XP, Vista and Windows 7, free rainbow tables are also available.

A live CD of OphCrack is also available to simplify the cracking. One can use the Live CD of OphCrack to crack Windows-based passwords. This tool is available for free.

9. L0phtCrack

L0phtCrack is an alternative to OphCrack. It attempts to crack Windows passwords from hashes. For cracking passwords, it uses Windows workstations, network servers, primary domain controllers and Active Directory. It also uses dictionary and brute-force attacks for generating and guessing passwords. It was acquired by Symantec and discontinued in 2006. Later, L0pht developers again reacquired it and launched L0phtCrack in 2009.

L0phtCrack also comes with the ability to scan routine password security scans. One can set daily, weekly or monthly audits, and it will start scanning at the scheduled time.

Learn about L0phtCrack here.

10. Aircrack-ng

Aircrack-ng is a Wi-Fi password-cracking tool that can crack WEP or WPA/WPA2 PSK passwords. It analyzes wireless encrypted packets and then tries to crack passwords via the dictionary attacks and the PTW, FMS and other cracking algorithms. It is available for Linux and Windows systems. A live CD of Aircrack is also available.


How to create a password that’s hard to crack

In this post, we have listed 10 password-cracking tools. These tools try to crack passwords with different password-cracking algorithms. Most of the password cracking tools are available for free. So, you should always try to have a strong password that is hard to crack. These are a few tips you can try while creating a password.

The longer the password, the harder it is to crack: Password length is the most important factor. The complexity of a brute force password guessing attack grows exponentially with the length of the password. A random seven-character password can be cracked in minutes, while a ten-character one takes hundreds of years.
Always use a combination of characters, numbers and special characters: Using a variety of characters also makes brute-force password-guessing more difficult, since it means that crackers need to try a wider variety of options for each character of the password. Incorporate numbers and special characters and not just at the end of the password or as a letter substitution (like @ for a).
Variety in passwords: Credential stuffing attacks use bots to test if passwords stolen from one online account are also used for other accounts. A data breach at a tiny company could compromise a bank account if the same credentials are used. Use a long, random, and unique password for all online accounts.