Browser Extensions

Adversaries may abuse Internet browser extensions to establish persistent access to victim systems. Browser extensions or plugins are small programs that can add functionality and customize aspects of Internet browsers. They can be installed directly or through a browser's app store and generally have access and permissions to everything that the browser can access.(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.

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](https://attack.mitre.org/tactics/TA0011).(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 [Defense Evasion](https://attack.mitre.org/tactics/TA0005).(Citation: Browers FriarFox)(Citation: Browser Adrozek) 

Platforms: Linux
macOS
Windows
Tactics:
phase_name: persistence

Detection:
Inventory and monitor browser extension installations that deviate from normal, expected, and benign extensions. Process and network monitoring can be used to detect browsers communicating with a C2 server. However, this may prove to be a difficult way of initially detecting a malicious extension depending on the nature and volume of the traffic it generates.

Monitor for any new items written to the Registry or PE files written to disk. That may correlate with browser extension installation.

On macOS, monitor the command line for usage of the profiles tool, such as <code>profiles install -type=configuration</code>. Additionally, all installed extensions maintain a <code>plist</code> file in the <code>/Library/Managed Preferences/username/</code> directory. Ensure all listed files are in alignment with approved extensions.(Citation: xorrior chrome extensions macOS)

References:
source_name: mitre-attack
description: Brinkmann, M. (2017, September 19). First Chrome extension with JavaScript Crypto Miner detected. Retrieved November 16, 2017.
source_name: Chrome Extension Crypto Miner
description: Chris Ross. (2019, February 8). No Place Like Chrome. Retrieved April 27, 2021.
source_name: xorrior chrome extensions macOS
description: Chrome. (n.d.). What are Extensions?. Retrieved November 16, 2017.
source_name: Chrome Extensions Definition
description: De Tore, M., Warner, J. (2018, January 15). MALICIOUS CHROME EXTENSIONS ENABLE CRIMINALS TO IMPACT OVER HALF A MILLION USERS AND GLOBAL BUSINESSES. Retrieved January 17, 2018.
source_name: ICEBRG Chrome Extensions
description: Jagpal, N., et al. (2015, August). Trends and Lessons from Three Years Fighting Malicious Extensions. Retrieved November 17, 2017.
source_name: Malicious Chrome Extension Numbers
description: Kjaer, M. (2016, July 18). Malware in the browser: how you might get hacked by a Chrome extension. Retrieved November 22, 2017.
source_name: Chrome Extension C2 Malware
description: Marinho, R. (n.d.). "Catch-All" Google Chrome Malicious Extension Steals All Posted Data. Retrieved November 16, 2017.
source_name: Catch All Chrome Extension
description: Marinho, R. (n.d.). (Banker(GoogleChromeExtension)).targeting. Retrieved November 18, 2017.
source_name: Banker Google Chrome Extension Steals Creds
description: Microsoft Threat Intelligence. (2020, December 10). Widespread malware campaign seeks to silently inject ads into search results, affects multiple browsers. Retrieved February 26, 2024.
source_name: Browser Adrozek
description: Raggi, Michael. Proofpoint Threat Research Team. (2021, February 25). TA413 Leverages New FriarFox Browser Extension to Target the Gmail Accounts of Global Tibetan Organizations. Retrieved February 26, 2024.
source_name: Browers FriarFox
description: Vachon, F., Faou, M. (2017, July 20). Stantinko: A massive adware campaign operating covertly since 2012. Retrieved November 16, 2017.
source_name: Stantinko Botnet
description: Wikipedia. (2017, October 8). Browser Extension. Retrieved January 11, 2018.
source_name: Wikipedia Browser Extension