Browser Extensions

Executive Summary

Browser Extensions (T1176.001) is a MITRE ATT&CK technique associated with Persistence. Adversaries may abuse internet browser extensions to establish persistent access to victim systems.

Why Attackers Use It

Attackers use Browser Extensions because it provides a reliable way to advance their objective within the Persistence tactic, often with a favorable balance of impact versus detectability on Linux, Windows, macOS environments. Defenders should assess this behavior in the context of the affected platform and adjacent activity rather than treating it as a standalone indicator.

MITRE Description

Adversaries may abuse internet browser extensions to establish persistent access to victim systems. Browser extensions or plugins are small programs that can add functionality to and customize aspects of internet browsers. They can be installed directly via a local file or custom URL or through a browser's app store - an official online platform where users can browse, install, and manage extensions for a specific web browser. Extensions generally inherit the web browser's permissions previously granted.(Citation: Wikipedia Browser Extension)(Citation: Chrome Extensions Definition)

Malicious extensions can be installed into a browser through malicious app store downloads masquerading as legitimate extensions, through social engineering, or by an adversary that has already compromised a system. Security can be limited on browser app stores, so it may not be difficult for malicious extensions to defeat automated scanners.(Citation: Malicious Chrome Extension Numbers) Depending on the browser, adversaries may also manipulate an extension's update url to install updates from an adversary-controlled server or manipulate the mobile configuration file to silently install additional extensions.

Adversaries may abuse how chromium-based browsers load extensions by modifying or replacing the Preferences and/or Secure Preferences files to silently install malicious extensions. When the browser is not running, adversaries can alter these files, ensuring the extension is loaded, granted desired permissions, and will persist in browser sessions. This method does not require user consent and extensions are silently loaded in the background from disk or from the browser's trusted store.(Citation: Pulsedive)

Previous to macOS 11, adversaries could silently install browser extensions via the command line using the <code>profiles</code> tool to install malicious <code>.mobileconfig</code> files. In macOS 11+, the use of the <code>profiles</code> tool can no longer install configuration profiles; however, <code>.mobileconfig</code> files can be planted and installed with user interaction.(Citation: xorrior chrome extensions macOS)

Once the extension is installed, it can browse to websites in the background, steal all information that a user enters into a browser (including credentials), and be used as an installer for a RAT for persistence.(Citation: Chrome Extension Crypto Miner)(Citation: ICEBRG Chrome Extensions)(Citation: Banker Google Chrome Extension Steals Creds)(Citation: Catch All Chrome Extension)

There have also been instances of botnets using a persistent backdoor through malicious Chrome extensions for Command and Control.(Citation: Stantinko Botnet)(Citation: Chrome Extension C2 Malware) Adversaries may also use browser extensions to modify browser permissions and components, privacy settings, and other security controls for Stealth.(Citation: Browers FriarFox)(Citation: Browser Adrozek)

Attack Flow

1. Attacker gains the prerequisite access or context described below.
2. Attacker executes Browser Extensions to achieve its tactical objective (Persistence).
3. Resulting access/data/effect is leveraged to advance the broader attack chain (see Related Techniques).

Prerequisites

• Platform(s): Linux, Windows, macOS
• ATT&CK does not define one universal permission requirement for this technique. Establish the required access from the observed implementation and affected platform.

Common Tools

• Tool attribution is implementation-specific. Use ATT&CK procedure examples and local telemetry to identify the binaries, services, scripts, accounts, or cloud resources involved.

Commands

No universal command represents Browser Extensions. Capture the exact command line, arguments, parent process, account, host, and execution time from the investigated environment; do not operationalize unverified examples.

Network Traffic

• Network observability is implementation-dependent. Review DNS, proxy, firewall, flow, authentication, and packet telemetry around the activity window, then correlate remote endpoints and protocol behavior with host evidence.

Windows Events

Sysmon Events

Detection Opportunities

No MITRE detection guidance published for this technique.

Relevant ATT&CK Data Sources: N/A

Sigma Rules

A universal Sigma rule would create unreliable results because this technique has no single guaranteed observable. Build detection logic from a documented behavior and supported data source, scope it to the affected platform, and validate it against benign administrative activity before deployment.

Splunk Queries

Start with the data sources named in the detection section. Scope searches by asset, identity, and time window; correlate the primary behavior with preceding access and subsequent actions. A portable query is intentionally not provided where the technique lacks a universal schema or observable.

Investigation Workflow

1. Confirm that the observed behavior is consistent with Browser Extensions and rule out expected administrative or application activity.
2. Establish the first-seen time, initiating identity, source system, target system, and affected resources.
3. Collect relevant host, identity, network, cloud, and application telemetry for the surrounding time window.
4. Correlate parent and child activity, remote connections, file or configuration changes, and related ATT&CK techniques.
5. Determine scope by searching for the same observable across peer assets and identities.
6. Preserve volatile evidence and record confidence, assumptions, and telemetry gaps before containment.

Containment

1. Isolate affected host(s)/account(s) identified during investigation.
2. Revoke or rotate any credentials/tokens potentially exposed.
3. Apply the mitigations listed below where not already enforced.
4. Validate no related techniques (see Related Techniques) were chained against the same asset.

Mitigation

• M1033 -- Limit Software Installation: Prevent users or groups from installing unauthorized or unapproved software to reduce the risk of introducing malicious or vulnerable applications.
• M1047 -- Audit: Auditing is the process of recording activity and systematically reviewing and analyzing the activity and system configurations.
• M1051 -- Update Software: Software updates ensure systems are protected against known vulnerabilities by applying patches and upgrades provided by vendors.
• M1017 -- User Training: User Training involves educating employees and contractors on recognizing, reporting, and preventing cyber threats that rely on human interaction, such as phishing, social engineering, and other manipulative techniques.
• M1038 -- Execution Prevention: Prevent the execution of unauthorized or malicious code on systems by implementing application control, script blocking, and other execution prevention mechanisms.

Related Techniques

• T1036.005
• T1041
• T1071.001
• T1082
• T1113
• T1140
• T1176
• T1204.002
• T1555.003