Suspicious Browser Child Process

Identifies the execution of a suspicious browser child process. Adversaries may gain access to a system through a user visiting a website over the normal course of browsing. With this technique, the user’s web browser is typically targeted for exploitation.

Rule type: eql

Rule indices:

logs-endpoint.events.*

Severity: high

Risk score: 73

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Domain: Endpoint
OS: macOS
Use Case: Threat Detection
Tactic: Initial Access
Tactic: Execution
Data Source: Elastic Defend

Version: 107

Rule authors:

Elastic

Rule license: Elastic License v2

Setup

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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.

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.
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.
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.

Rule query

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process where host.os.type == "macos" and event.type in ("start", "process_started") and
  process.parent.name : ("Google Chrome", "Google Chrome Helper*", "firefox", "Opera", "Safari", "com.apple.WebKit.WebContent", "Microsoft Edge") and
  process.name : ("sh", "bash", "dash", "ksh", "tcsh", "zsh", "curl", "wget", "python*", "perl*", "php*", "osascript", "pwsh") and
  process.command_line != null and
  not process.command_line : "*/Library/Application Support/Microsoft/MAU*/Microsoft AutoUpdate.app/Contents/MacOS/msupdate*" and
  not process.args :
    (
      "hw.model",
      "IOPlatformExpertDevice",
      "/Volumes/Google Chrome/Google Chrome.app/Contents/Frameworks/*/Resources/install.sh",
      "/Applications/Google Chrome.app/Contents/Frameworks/Google Chrome Framework.framework/Versions/*/Helpers/Google Chrome Helper (Renderer).app/Contents/MacOS/Google Chrome Helper (Renderer)",
      "/Applications/Firefox.app/Contents/MacOS/plugin-container.app/Contents/MacOS/plugin-container",
      "--defaults-torrc",
      "*Chrome.app",
      "Framework.framework/Versions/*/Resources/keystone_promote_preflight.sh",
      "/Users/*/Library/Application Support/Google/Chrome/recovery/*/ChromeRecovery",
      "$DISPLAY",
      "*GIO_LAUNCHED_DESKTOP_FILE_PID=$$*",
      "/opt/homebrew/*",
      "/usr/local/*brew*"
    )

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
Technique:
- Name: Exploitation for Client Execution
- ID: T1203
- Reference URL: https://attack.mitre.org/techniques/T1203/
Tactic:
- Name: Initial Access
- ID: TA0001
- Reference URL: https://attack.mitre.org/tactics/TA0001/
Technique:
- Name: Drive-by Compromise
- ID: T1189
- Reference URL: https://attack.mitre.org/techniques/T1189/

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