persistence_screensaver_plist_file_modification.toml

[metadata]
creation_date = "2021/10/05"
integration = ["endpoint"]
maturity = "production"
updated_date = "2024/05/21"

[rule]
author = ["Elastic"]
description = """
Identifies when a screensaver plist file is modified by an unexpected process. An adversary can maintain persistence on
a macOS endpoint by creating a malicious screensaver (.saver) file and configuring the screensaver plist file to execute
code each time the screensaver is activated.
"""
from = "now-9m"
index = ["logs-endpoint.events.*"]
language = "eql"
license = "Elastic License v2"
name = "Screensaver Plist File Modified by Unexpected Process"
note = """## Triage and analysis

- Analyze the plist file modification event to identify whether the change was expected or not
- Investigate the process that modified the plist file for malicious code or other suspicious behavior
- Identify if any suspicious or known malicious screensaver (.saver) files were recently written to or modified on the host
"""
references = [
    "https://posts.specterops.io/saving-your-access-d562bf5bf90b",
    "https://github.com/D00MFist/PersistentJXA",
]
risk_score = 47
rule_id = "e6e8912f-283f-4d0d-8442-e0dcaf49944b"
setup = """## Setup

This rule requires data coming in from Elastic Defend.

### Elastic Defend Integration Setup
Elastic Defend is integrated into the Elastic Agent using Fleet. Upon configuration, the integration allows the Elastic Agent to monitor events on your host and send data to the Elastic Security app.

#### Prerequisite Requirements:
- Fleet is required for Elastic Defend.
- To configure Fleet Server refer to the [documentation](https://www.elastic.co/guide/en/fleet/current/fleet-server.html).

#### The following steps should be executed in order to add the Elastic Defend integration on a macOS System:
- Go to the Kibana home page and click "Add integrations".
- In the query bar, search for "Elastic Defend" and select the integration to see more details about it.
- Click "Add Elastic Defend".
- Configure the integration name and optionally add a description.
- Select the type of environment you want to protect, for MacOS it is recommended to select "Traditional Endpoints".
- Select a configuration preset. Each preset comes with different default settings for Elastic Agent, you can further customize these later by configuring the Elastic Defend integration policy. [Helper guide](https://www.elastic.co/guide/en/security/current/configure-endpoint-integration-policy.html).
- We suggest selecting "Complete EDR (Endpoint Detection and Response)" as a configuration setting, that provides "All events; all preventions"
- Enter a name for the agent policy in "New agent policy name". If other agent policies already exist, you can click the "Existing hosts" tab and select an existing policy instead.
For more details on Elastic Agent configuration settings, refer to the [helper guide](https://www.elastic.co/guide/en/fleet/current/agent-policy.html).
- Click "Save and Continue".
- To complete the integration, select "Add Elastic Agent to your hosts" and continue to the next section to install the Elastic Agent on your hosts.
For more details on Elastic Defend refer to the [helper guide](https://www.elastic.co/guide/en/security/current/install-endpoint.html).
"""
severity = "medium"
tags = [
    "Domain: Endpoint",
    "OS: macOS",
    "Use Case: Threat Detection",
    "Tactic: Persistence",
    "Data Source: Elastic Defend",
]
timestamp_override = "event.ingested"
type = "eql"

query = '''
file where host.os.type == "macos" and event.type != "deletion" and
  file.name: "com.apple.screensaver.*.plist" and
   file.path : (
      "/Users/*/Library/Preferences/ByHost/*",
      "/Library/Managed Preferences/*",
      "/System/Library/Preferences/*"
      ) and
  (
    process.code_signature.trusted == false or
    process.code_signature.exists == false or

    /* common script interpreters and abused native macOS bins */
    process.name : (
      "curl",
      "mktemp",
      "tail",
      "funzip",
      "python*",
      "osascript",
      "perl"
      )
   ) and

  /* Filter OS processes modifying screensaver plist files */
  not process.executable : (
    "/usr/sbin/cfprefsd",
    "/usr/libexec/xpcproxy",
    "/System/Library/CoreServices/ManagedClient.app/Contents/Resources/MCXCompositor",
    "/System/Library/CoreServices/ManagedClient.app/Contents/MacOS/ManagedClient"
    )
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1546"
name = "Event Triggered Execution"
reference = "https://attack.mitre.org/techniques/T1546/"


[rule.threat.tactic]
id = "TA0003"
name = "Persistence"
reference = "https://attack.mitre.org/tactics/TA0003/"