>chmod
Chmod alters file mode bits. SUID or sudo chmod is abused to turn standard shells into persistent SUID root binaries by adding the 4755 permission bit.
Default Executable Paths
/bin/chmod/usr/bin/chmodIntegrity & Metadata
Setting SUID bit on /bin/bash or /bin/dash creates an immediate elevation backdoor.
Monitor chmod commands assigning SUID/SGID bits (u+s, 4755, 4777) to shell executables or interpreters.
Executive Summary & AI Quick Reference
chmod is a native utility pre-installed on Linux systems. Threat actors and red teams abuse chmod as a Living-off-the-Land Binary (LOLBin) to achieve Defense Evasion without triggering traditional antivirus file-hash alerts. Legitimate system administrators use it for routine administration, making behavioral command-line telemetry essential for differentiation.
Weaponized Parameters & Proof-of-Concepts
Documented attack commands, parameter flags, and privilege prerequisites.
Assigns the SUID permission bit to a shell interpreter to enable persistent unprivileged root access.
chmod 4755 /bin/dashSIEM & EDR Detection Rules
Production telemetry rules configured for Microsoft Defender, Sigma, and Splunk.
Telemetry & SIEM Detection Suite (chmod)
Validated against MITRE T1548.0011DeviceProcessEvents | where FileName =~ "chmod" | where ProcessCommandLine has_any ("4755", "u+s", "+s", "4777") and ProcessCommandLine has_any ("/bin/", "/usr/bin/", "sh", "bash", "dash") | project Timestamp, DeviceName, AccountName, ProcessCommandLineMitigation, Hardening & Prevention
Recommended defensive controls to block or constrain chmod abuse.
Audit and remove unnecessary SUID / SGID bits (`chmod u-s /path/to/$chmod`) and restrict sudoers NOPASSWD execution grants.
Implement AppArmor or SELinux profiles restricting chmod network socket creation and read access to sensitive user directories.
Deploy the KQL, Sigma, and Splunk detection queries below. Alert on anomalous child processes, web requests to unrated external IPs, or encoded payload strings.
Frequently Asked Questions (FAQ) • chmod
Key operational questions and defensive answers about chmod LOLBin tradecraft.
What is chmod and why is it classified as a LOLBin?
chmod is a legitimate, pre-installed or trusted utility on Linux. It is classified as a Living-off-the-Land Binary (LOLBin) because adversaries abuse its built-in functionality to perform malicious operations—such as Defense Evasion—without dropping custom malware binaries on disk.
How do threat actors abuse chmod in cyber intrusions?
Adversaries leverage chmod to execute stealthy actions while evading signature-based security controls. For example, attackers execute commands like "chmod 4755 /bin/dash" to achieve Defense Evasion, masquerading behind legitimate system process lineage.
How can SOC analysts detect suspicious chmod activity?
Detection engineers monitor process creation events (Windows Event ID 4688 or Sysmon Event ID 1; Linux auditd EXECVE; macOS Endpoint Security) inspecting anomalous command line arguments, unusual parent-child process relationships (e.g. Office apps or web servers spawning chmod), and unexpected network connections.
What MITRE ATT&CK techniques does chmod map to?
chmod maps to MITRE ATT&CK technique(s): T1548.001. These techniques cover adversary actions across tactics such as Defense Evasion, Execution, Persistence, and Command and Control.
How can organizations mitigate and restrict chmod?
Mitigation strategies include implementing Application Control policies (AppLocker or Windows Defender Application Control - WDAC), enforcing Attack Surface Reduction (ASR) rules, configuring strict privilege separation (disallowing standard users from running sensitive switches), and alerting on execution from non-standard directories.
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