/etc/passwd and /etc/shadow (T1003.008)

Description

Adversaries may attempt to dump the contents of /etc/passwd and /etc/shadow to enable offline password cracking. Most modern Linux operating systems use a combination of /etc/passwd and /etc/shadow to store user account information, including password hashes in /etc/shadow. By default, /etc/shadow is only readable by the root user.(Citation: Linux Password and Shadow File Formats)

Linux stores user information such as user ID, group ID, home directory path, and login shell in /etc/passwd. A “user” on the system may belong to a person or a service. All password hashes are stored in /etc/shadow - including entries for users with no passwords and users with locked or disabled accounts.(Citation: Linux Password and Shadow File Formats)

Adversaries may attempt to read or dump the /etc/passwd and /etc/shadow files on Linux systems via command line utilities such as the cat command.(Citation: Arctic Wolf) Additionally, the Linux utility unshadow can be used to combine the two files in a format suited for password cracking utilities such as John the Ripper - for example, via the command /usr/bin/unshadow /etc/passwd /etc/shadow > /tmp/crack.password.db(Citation: nixCraft - John the Ripper). Since the user information stored in /etc/passwd are linked to the password hashes in /etc/shadow, an adversary would need to have access to both.