OS Credential Dumping: /etc/passwd and /etc/shadow

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.[1]

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:[2] # /usr/bin/unshadow /etc/passwd /etc/shadow > /tmp/crack.password.db

ID: T1003.008
Sub-technique of:  T1003
Platforms: Linux
Permissions Required: root
Version: 1.0
Created: 11 February 2020
Last Modified: 20 March 2020
Provided by LAYER 8

Procedure Examples

ID Name Description
S0349 LaZagne

LaZagne can obtain credential information from /etc/shadow using the shadow.py module.[3]


ID Mitigation Description
M1027 Password Policies

Ensure that root accounts have complex, unique passwords across all systems on the network.

M1026 Privileged Account Management

Follow best practices in restricting access to privileged accounts to avoid hostile programs from accessing such sensitive information.


ID Data Source Data Component
DS0017 Command Command Execution
DS0022 File File Access

The AuditD monitoring tool, which ships stock in many Linux distributions, can be used to watch for hostile processes attempting to access /etc/passwd and /etc/shadow, alerting on the pid, process name, and arguments of such programs.