Password Attackspasswordcrackingunixcryptmd5vulnerability

Crack

Crack is a password guessing program that quickly locates vulnerabilities in Unix or other password files by scanning for weak login passwords. It provides variants for crypt() and MD5 password hashing.

Description

Crack is designed to scan the contents of password files to identify users with weak login passwords. It helps uncover misguidedly chosen passwords that pose security risks in Unix or similar systems. The tool includes runtime files for both crypt() and MD5 variants, along with common files shared across versions.

Use cases include auditing password strength in password files to find easily guessable passwords. The package provides programs like Crack for the guessing process and Crack-Reporter for summarizing results, such as passwords cracked and errors encountered.

The crack-common package supplies shared files for all variants, while crack and crack-md5 offer specific runtime components. Dependencies ensure compatibility with standard libraries like libc6 and libcrypt1.

How It Works

Crack scans password files, testing entries against a dictionary or guessing logic to identify weak passwords using crypt() or MD5 hashing variants. It processes files specified with options and formats, generating reports via Crack-Reporter on cracked passwords, timestamps, errors, and warnings.

Installation

bash
sudo apt install crack

Flags

[options]Options for Crack usage
[bindir]Optional bindir argument
[-fmt format]Specify password format
[files]Password files to process

Examples

Shows usage: Crack [options] [bindir] [[-fmt format] files]...
Crack -h
Runs the main Crack password guessing program
Crack
Displays sample report output with cracked passwords timestamp, errors, and done status
Crack-Reporter -h
Generates report showing passwords cracked with timestamp and completion status
Crack-Reporter
Installs the crypt() variant of Crack
sudo apt install crack
Installs the MD5 variant of Crack
sudo apt install crack-md5
Installs common files for all Crack variants
sudo apt install crack-common
Updated 2026-04-16kali.org ↗