T1037.005 Startup Items

> Sub-technique of: T1037

High-Level Description

Adversaries may use startup items automatically executed at boot initialization to establish persistence. Startup items execute during the final phase of the boot process and contain shell scripts or other executable files along with configuration information used by the system to determine the execution order for all startup items.

This is technically a deprecated technology (superseded by Launch Daemon), and thus the appropriate folder, <code>/Library/StartupItems</code> isn’t guaranteed to exist on the system by default, but does appear to exist by default on macOS Sierra. A startup item is a directory whose executable and configuration property list (plist), <code>StartupParameters.plist</code>, reside in the top-level directory.

An adversary can create the appropriate folders/files in the StartupItems directory to register their own persistence mechanism. Additionally, since StartupItems run during the bootup phase of macOS, they will run as the elevated root user.

Kill Chain Phase

• Persistence (TA0003)
• Privilege Escalation (TA0004)

Platforms: macOS

What to Check

• ] Identify if Startup Items technique is applicable to target environment
• ] Check macOS systems for indicators of Startup Items
• ] Verify mitigations are bypassed or absent (1 known mitigations)
• ] Assess detection coverage (1 detection strategies)

How to Test

Atomic Red Team Tests

The following tests are from Atomic Red Team and provide actionable ways to test this technique:

Atomic Test 1: Add file to Local Library StartupItems

Modify or create an file in /Library/StartupItems Reference

Supported Platforms: macos Elevation Required: Yes

bash
sudo touch /Library/StartupItems/EvilStartup.plist

Atomic Test 2: Add launch script to launch daemon

Add launch script to /Library/StartupItems to launch agent Example

Supported Platforms: macos Elevation Required: Yes

bash
sudo cp #{path_startup_params} /Library/StartupItems/StartupParameters.plist
sudo cp #{path_malicious_script} /Library/StartupItems/atomic.sh
sudo cp #{path_malicious_plist} /tmp/T1037_005_daemon.plist
sudo /Library/StartupItems/atomic.sh start

Dependencies:

• /Library/StartupItems must exist
• The shared library must exist on disk at specified location (#{path_malicious_plist})
• The startup script must exist on disk at specified location (#{path_malicious_script})

Atomic Test 3: Add launch script to launch agent

Add launch script to /Library/StartupItems to launch agent Example

Supported Platforms: macos Elevation Required: Yes

bash
sudo cp #{path_startup_params} /Library/StartupItems/StartupParameters.plist
sudo cp #{path_malicious_script} /Library/StartupItems/atomic.sh
sudo cp #{path_malicious_plist} /tmp/T1037_005_agent.plist
/Library/StartupItems/atomic.sh start

Dependencies:

• /Library/StartupItems must exist
• The shared library must exist on disk at specified location (#{path_malicious_plist})
• The startup script must exist on disk at specified location (#{path_malicious_script})

Manual Testing

If Atomic Red Team tests are not applicable, manually verify the technique by:

1. Identify Attack Surface: Determine if the target environment is susceptible to Startup Items by examining the target platforms (macOS).

1. Assess Existing Defenses: Review whether mitigations for T1037.005 are in place. If defenses are absent or misconfigured, this technique may be exploitable.

1. Execute Test: Use tools and methods described in the MITRE ATT&CK page and external references below.

Remediation Guide

M1022 Restrict File and Directory Permissions

Since StartupItems are deprecated, preventing all users from writing to the <code>/Library/StartupItems</code> directory would prevent any startup items from getting registered.

Detection

Detect Modification of macOS Startup Items

Risk Assessment

| Finding | Severity | Impact | | ---------------------------------- | -------- | ----------- | | Startup Items technique applicable | Low | Persistence |

CWE Categories

| CWE ID | Title | | ------- | ----------------------------- | | CWE-276 | Incorrect Default Permissions |

References

• Startup Items
• Methods of Mac Malware Persistence
• Atomic Red Team - T1037.005
• MITRE ATT&CK - T1037.005