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Boot or Logon Initialization Scripts: RC Scripts

ID Name
T1037.001 Logon Script (Windows)
T1037.002 Login Hook
T1037.003 Network Logon Script
T1037.004 RC Scripts
T1037.005 Startup Items

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.[1][2] 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.[3]

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. [4][5] This technique can be used on Mac OS X Panther v10.3 and earlier versions which still execute the RC scripts.[6] To maintain backwards compatibility some systems, such as Ubuntu, will execute the RC scripts if they exist with the correct file permissions.[7]

ID: T1037.004
Sub-technique of:  T1037
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Platforms: Linux, macOS
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Permissions Required: root
Version: 2.0
Created: 15 January 2020
Last Modified: 27 April 2021

Procedure Examples

ID Name Description
S0687 Cyclops Blink

Cyclops Blink has the ability to execute on device startup, using a modified RC script named S51armled.[8]
S0690 Green Lambert

Green Lambert can add init.d and rc.d files in the /etc folder to establish persistence.[9][10]

S0394 HiddenWasp

HiddenWasp installs reboot persistence by adding itself to /etc/rc.local.[2]
S0278 iKitten

iKitten adds an entry to the rc.common file for persistence.[11]

Mitigations

ID Mitigation Description
M1022 Restrict File and Directory Permissions

Limit privileges of user accounts so only authorized users can edit the rc.common file.

Detection

ID Data Source Data Component
DS0017 Command Command Execution
DS0022 File File Creation
File Modification
DS0009 Process Process Creation

Monitor for unexpected changes to RC scripts in the /etc/ directory. Monitor process execution resulting from RC scripts for unusual or unknown applications or behavior.

Monitor for /etc/rc.local file creation. Although types of RC scripts vary for each Unix-like distribution, several execute /etc/rc.local if present.

References

  1. Iran Threats . (2017, December 5). Flying Kitten to Rocket Kitten, A Case of Ambiguity and Shared Code. Retrieved May 28, 2020.
  2. Sanmillan, I. (2019, May 29). HiddenWasp Malware Stings Targeted Linux Systems. Retrieved June 24, 2019.
  3. Paul Litvak. (2020, May 4). Kaiji: New Chinese Linux malware turning to Golang. Retrieved December 17, 2020.
  4. Apple. (2016, September 13). Daemons and Services Programming Guide - Creating Launch Daemons and Agents. Retrieved February 24, 2021.
  5. Apple. (2016, September 13). Startup Items. Retrieved July 11, 2017.
  6. Patrick Wardle. (2014, September). Methods of Malware Persistence on Mac OS X. Retrieved July 5, 2017.
  1. Canonical Ltd.. (n.d.). systemd-rc-local-generator - Compatibility generator for starting /etc/rc.local and /usr/sbin/halt.local during boot and shutdown. Retrieved February 23, 2021.
  2. NCSC. (2022, February 23). Cyclops Blink Malware Analysis Report. Retrieved March 3, 2022.
  3. Sandvik, Runa. (2021, October 1). Made In America: Green Lambert for OS X. Retrieved March 21, 2022.
  4. Sandvik, Runa. (2021, October 18). Green Lambert and ATT&CK. Retrieved March 21, 2022.
  5. Patrick Wardle. (n.d.). Mac Malware of 2017. Retrieved September 21, 2018.