T1036.012 Browser Fingerprint

> Sub-technique of: T1036

High-Level Description

Adversaries may attempt to blend in with legitimate traffic by spoofing browser and system attributes like operating system, system language, platform, user-agent string, resolution, time zone, etc. The HTTP User-Agent request header is a string that lets servers and network peers identify the application, operating system, vendor, and/or version of the requesting user agent.

Adversaries may gather this information through System Information Discovery or by users navigating to adversary-controlled websites, and then use that information to craft their web traffic to evade defenses.

Kill Chain Phase

• Defense Evasion (TA0005)

Platforms: Linux, macOS, Windows

What to Check

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

How to Test

Manual Testing

1. Identify Attack Surface: Determine if the target environment is susceptible to Browser Fingerprint by examining the target platforms (Linux, macOS, Windows).

1. Assess Existing Defenses: Review whether mitigations for T1036.012 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.

> Note: No Atomic Red Team tests available for this technique. See Atomic Red Team GitHub for updates.

Remediation Guide

M1047 Audit

Review and limit the fingerprinting surface to only necessary information on each browser to make the browser less unique. For example, the available fonts may be limited to a standard font list.

Detection

Detection of Spoofed User-Agent

Risk Assessment

| Finding | Severity | Impact | | ---------------------------------------- | -------- | --------------- | | Browser Fingerprint technique applicable | Medium | Defense Evasion |

CWE Categories

| CWE ID | Title | | ------- | ---------------------------- | | CWE-693 | Protection Mechanism Failure |

References

• Mozilla User Agent
• Gummy Browsers: Targeted Browser Spoofing against State-of-the-Art Fingerprinting Techniques
• Atomic Red Team - T1036.012
• MITRE ATT&CK - T1036.012