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ATT&CK Technique

RC Scripts

T1037.004 · persistence, privilege-escalation

Adversaries may establish persistence by modifying RC scripts, which are executed during a Unix-like system’s startup. These files allow system administrators to map and start custom services at startup for different run levels. RC scripts require root privileges to modify.

Adversaries may establish persistence by adding a malicious binary path or shell commands to rc.local, rc.common, and other RC scripts specific to the Unix-like distribution. Upon reboot, the system executes the script's contents as root, resulting in persistence. Adversary abuse of RC scripts is especially effective for lightweight Unix-like distributions using the root user as default, such as ESXi hypervisors, IoT, or embedded systems.

As ESXi servers store most system files in memory and therefore discard changes on shutdown, leveraging /etc/rc.local.d/local.sh is one of the few mechanisms for enabling persistence across reboots. Several Unix-like systems have moved to Systemd and deprecated the use of RC scripts. This is now a deprecated mechanism in macOS in favor of Launchd.

This technique can be used on Mac OS X Panther v10.3 and earlier versions which still execute the RC scripts. To maintain backwards compatibility some systems, such as Ubuntu, will execute the RC scripts if they exist with the correct file permissions.

macOSLinuxNetwork DevicesESXi
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Actors Using This

1
russiaAPT29
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Atomic Tests

3
Executable Atomic Red Team test cases for exercising this technique in a lab. Copy a command, run it on the listed platform, confirm your detections fire.
bashelevatedmacosrc.common
Modify rc.common [Reference](https://developer.apple.com/library/content/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/StartupItems.html) 
sudo echo osascript -e 'tell app "Finder" to display dialog "Hello World"' >> /etc/rc.common
bashelevatedlinuxrc.common
Modify rc.common 
filename='/etc/rc.common';if [ ! -f $filename ];then sudo touch $filename;else sudo cp $filename /etc/rc.common.original;fi
printf '%s\n' '#!/bin/bash' | sudo tee /etc/rc.common
echo "python3 -c \"import os, base64;exec(base64.b64decode('aW1wb3J0IG9zCm9zLnBvcGVuKCdlY2hvIGF0b21pYyB0ZXN0IGZvciBtb2RpZnlpbmcgcmMuY29tbW9uID4gL3RtcC9UMTAzNy4wMDQucmMuY29tbW9uJykK'))\"" | sudo tee -a /etc/rc.common
printf '%s\n' 'exit 0' | sudo tee -a /etc/rc.common
sudo chmod +x /etc/rc.common
shelevatedlinuxrc.local
Modify rc.local 
filename='/etc/rc.local';if [ ! -f $filename ];then sudo touch $filename;else sudo cp $filename /etc/rc.local.original;fi
[ "$(uname)" = 'FreeBSD' ] && alias python3=python3.9 && printf '#\!/usr/local/bin/bash' | sudo tee /etc/rc.local || printf '#!/bin/bash' | sudo tee /etc/rc.local
echo "\npython3 -c \"import os, base64;exec(base64.b64decode('aW1wb3J0IG9zCm9zLnBvcGVuKCdlY2hvIGF0b21pYyB0ZXN0IGZvciBtb2RpZnlpbmcgcmMubG9jYWwgPiAvdG1wL1QxMDM3LjAwNC5yYy5sb2NhbCcpCgo='))\"" | sudo tee -a /etc/rc.local
printf 'exit 0' | sudo tee -a /etc/rc.local
sudo chmod +x /etc/rc.local
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Mitigations

1
MITRE ATT&CK mitigations - vendor-agnostic guidance for reducing exposure to this technique.
M1022Restrict File and Directory Permissions

Restricting file and directory permissions involves setting access controls at the file system level to limit which users, groups, or processes can read, write, or execute files. By configuring permissions appropriately, organizations can reduce the attack surface for adversaries seeking to access sensitive data, plant malicious code, or tamper with system files.

Enforce Least Privilege Permissions
  • Remove unnecessary write permissions on sensitive files and directories.
  • Use file ownership and groups to control access for specific roles. Example (Windows): Right-click the shared folder.
  • Properties.
  • Security tab.
  • Adjust permissions for NTFS ACLs.
Harden File Shares
  • Disable anonymous access to shared folders.
  • Enforce NTFS permissions for shared folders on Windows. Example: Set permissions to restrict write access to critical files, such as system executables (e.g., /bin or /sbin on Linux). Use tools like chown and chmod to assign file ownership and limit access. On Linux, apply: chmod 750 /etc/sensitive.conf `chown root:admin /etc/sensitive.
conf` File Integrity Monitoring (FIM)
  • Use tools like Tripwire, Wazuh, or OSSEC to monitor changes to critical file permissions.
Audit File System Access
  • Enable auditing to track permission changes or unauthorized access attempts.
  • Use auditd (Linux) or Event Viewer (Windows) to log activities.
Restrict Startup Directories
  • Configure permissions to prevent unauthorized writes to directories like C:\ProgramData\Microsoft\Windows\Start Menu. Example: Restrict write access to critical directories like /etc/, /usr/local/, and Windows directories such as C:\Windows\System32.
  • On Windows, use icacls to modify permissions: icacls "C:\Windows\System32" /inheritance:r /grant:r SYSTEM:(OI)(CI)F.
  • On Linux, monitor permissions using tools like lsattr or auditd.
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Detection Coverage

0/6 layers
Coverage across standard detection surfaces. Rows marked none have no rule of that type mapped. Some are real blind spots worth closing; others are simply not applicable to this technique (e.g. YARA matches malware files, not network behaviour).
Behavioral / log (Sigma) none
Analytics (MITRE CAR) none
Runtime / container (Falco) none
File / malware (YARA) none
Network (Suricata/Snort) none
Vuln scan (Nuclei) none
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