Detect Sudo and Sudo Caching in Splunk
Adversaries abuse sudo and sudo caching on Linux and macOS to execute commands with elevated privileges. Techniques include: modifying /etc/sudoers to grant NOPASSWD access, exploiting the sudo timestamp cache (default 15-minute window) to run commands without re-authentication, using 'sudo -n' to check if cached credentials exist, and exploiting sudoedit or sudo bypass vulnerabilities (CVE-2021-3156 Baron Samedit). ProtonB malware and various Linux post-exploitation frameworks abuse sudo for privilege escalation.
MITRE ATT&CK
- Technique
- T1548 Abuse Elevation Control Mechanism
- Sub-technique
- T1548.003 Sudo and Sudo Caching
- Canonical reference
- https://attack.mitre.org/techniques/T1548/003/
SPL Detection Query
index=linux_logs (sourcetype="linux_secure" OR sourcetype="syslog" OR sourcetype="auditd")
| eval detection_type=case(
sourcetype="auditd" AND match(_raw, "(?i)path.*(/etc/sudoers)") AND
match(_raw, "(?i)(write|open|truncate)"),
"Sudoers_File_Auditd_Write",
sourcetype="linux_secure" AND match(_raw, "(?i)(sudo|su).*COMMAND") AND
match(_raw, "(?i)(bash|sh|python|perl|ruby|/bin/\\*|ALL)"),
"Sudo_Shell_Command",
sourcetype="linux_secure" AND match(_raw, "(?i)sudo.*authentication failure") AND
match(_raw, "(?i)(-n|--non-interactive)"),
"Sudo_Failed_Cache_Check",
sourcetype="syslog" AND match(_raw, "(?i)NOPASSWD") AND
match(_raw, "(?i)(sudoers|visudo)"),
"Sudo_NOPASSWD_Config",
true(), null()
)
| where isnotnull(detection_type)
| table _time, host, user, detection_type, _raw
| sort - _timeDetects sudo abuse via Linux security logs. Auditd file write events on /etc/sudoers indicate unauthorized modification. Linux secure log sudo commands running shells (bash, sh, python) are escalation indicators. sudo -n authentication failures indicate cache probing. NOPASSWD strings in syslog/sudoers context indicate privilege grant.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Package manager sudo automation with -n flag
- Authorized administrative sudoers modifications
- Configuration management tool sudo usage
Other platforms for T1548.003
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 1List Current Sudo Privileges for Current User
Expected signal: Syslog/auditd: sudo -l command executed by current user. Auth log entry for sudo invocation.
- Test 2Add NOPASSWD Sudo Entry via sudoers.d
Expected signal: Auditd: file write event on /etc/sudoers.d/df00tech-test. Auth log: sudo cp command. Process creation for cp with /etc/sudoers.d path.
- Test 3Exploit Sudo Timestamp Cache
Expected signal: Syslog/auditd: sudo -n command with NOPASSWD check. Auth log entry. If successful: sudo COMMAND=whoami entry.
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