Detect /etc/passwd and /etc/shadow in IBM QRadar
Adversaries read /etc/passwd and /etc/shadow on Linux and Unix systems to extract password hashes for offline cracking. /etc/passwd contains usernames and user information (world-readable), while /etc/shadow contains the actual password hashes (root-readable only). Together they can be combined with `unshadow` and cracked with John the Ripper or Hashcat. Tools include LaZagne (shadow.py module), direct cat commands, and Python one-liners. Also includes reading from backup copies (/etc/shadow-, /etc/shadow.bak) and cloud instance metadata for default credentials. Used by multiple threat actors as a standard post-exploitation step on Linux systems.
MITRE ATT&CK
- Tactic
- Credential Access
- Technique
- T1003 OS Credential Dumping
- Sub-technique
- T1003.008 /etc/passwd and /etc/shadow
- Canonical reference
- https://attack.mitre.org/techniques/T1003/008/
QRadar Detection Query
SELECT
DATEFORMAT(devicetime, 'YYYY-MM-dd HH:mm:ss') AS event_time,
sourceip,
username,
"filename" AS accessed_file,
"process" AS process_name,
"command" AS command_line,
QIDNAME(qid) AS event_name,
CATEGORYNAME(category) AS category_name,
LOGSOURCETYPENAME(logsourceid) AS log_source_type,
CASE
WHEN "process" ILIKE ANY ('john','hashcat','unshadow','lazagne') THEN 'CRITICAL'
WHEN "process" ILIKE ANY ('python%','python3','perl','ruby','bash','sh','cat','cp','scp') THEN 'HIGH'
ELSE 'MEDIUM'
END AS risk_level
FROM events
WHERE
LOGSOURCETYPENAME(logsourceid) ILIKE ANY ('%Linux%', '%Syslog%', '%Auditd%', '%Universal CEF%')
AND (
(
"filename" IN ('/etc/shadow', '/etc/shadow-', '/etc/shadow.bak', '/etc/master.passwd', '/etc/security/passwd')
AND "process" NOT IN ('passwd', 'chpasswd', 'useradd', 'usermod', 'chage', 'login', 'newusers', 'shadow')
)
OR "command" ILIKE '%unshadow%'
OR (
"command" ILIKE '%lazagne%'
AND ("command" ILIKE '%shadow%' OR "command" ILIKE '%linux%' OR "command" ILIKE '%all%')
)
OR (
"command" ILIKE '%/etc/shadow%'
AND "command" ILIKE '%/etc/passwd%'
)
OR (
"process" ILIKE ANY ('john','hashcat')
AND "command" ILIKE '%shadow%'
)
OR (
"process" ILIKE ANY ('python%','python3','perl','ruby','cat','cp','scp','bash','sh')
AND "command" ILIKE '%/etc/shadow%'
)
)
ORDER BY devicetime DESC
LAST 24 HOURSDetects unauthorized access to /etc/shadow and related Linux credential files, and identifies execution of offline password cracking tools (unshadow, john, hashcat, lazagne). Queries QRadar events from Linux/Syslog/Auditd log sources and assigns risk tiers based on the accessing process.
Data Sources
Required Tables
False Positives & Tuning
- Root-level backup jobs (cron or backup agents) that archive /etc/ including shadow — these will fire unless the backup process name is explicitly excluded
- Automated compliance scanners (OpenSCAP, Nessus, Qualys) that read shadow file metadata or permissions during CIS benchmark checks
- Container image build processes that copy /etc/shadow into a new image layer when building hardened base images
- PAM module testing or custom authentication daemon development that opens /etc/shadow as part of integration tests in dev/staging environments
Other platforms for T1003.008
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Direct /etc/shadow Read with cat
Expected signal: Auditd file watch event (type=SYSCALL, syscall=openat) for /etc/shadow with exe=/bin/cat. DeviceFileEvents (if MDE Linux agent) for /etc/shadow read by cat. Process creation event for cat command with /etc/shadow argument.
- Test 2Unshadow and Password Hash Preparation
Expected signal: Auditd SYSCALL events for openat on both /etc/passwd and /etc/shadow with exe=/usr/bin/unshadow. File creation event for /tmp/atomic_hashes.txt. DeviceProcessEvents for unshadow execution. DeviceFileEvents for shadow and passwd access.
- Test 3LaZagne Linux Shadow Module
Expected signal: DeviceNetworkEvents for GitHub download connection. DeviceProcessEvents for lazagne execution with 'linux -shadow' arguments. Auditd openat events for /etc/shadow with exe=/tmp/lazagne. DeviceFileEvents for /etc/shadow access.
References (6)
- https://attack.mitre.org/techniques/T1003/008/
- https://github.com/AlessandroZ/LaZagne
- https://linux.die.net/man/8/unshadow
- https://www.openwall.com/john/
- https://linux-audit.com/monitoring-of-etc-shadow-using-linux-audit/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1003.008/T1003.008.md
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