Full Report
Whilst on a Red Team assessment back in 2015, we were faced with a tough Data Leak Protection (DLP) and web content management gateway system called Forcepoint TRITON. One of the goals, besides gaining full access to the client, was to see if sensitive data could be exfiltrated from the internal network to attacker controlled servers. The first logical step was to analyse how this device functioned and identify any flaws.
Analysis Summary
As a malware analyst and TTPs specialist, here is the summary derived from the provided context, focusing on the techniques used to bypass the Forcepoint TRITON system during the 2015 Red Team assessment.
# Tool/Technique: Abusing Forcepoint TRITON Web Categorization for Data Exfiltration and C2
## Overview
This describes a technique leveraged during a 2015 Red Team assessment to exfiltrate data and establish a Command and Control (C2) channel by exploiting the way the Forcepoint TRITON Web Content Gateway categorizes URLs, specifically targeting its automated web categorization feature.
## Technical Details
- Type: Technique (Security Control Bypass/Data Exfiltration)
- Platform: Microsoft Windows (Target host executing PowerShell)
- Capabilities: Bypassing DLP/Web Proxy controls to exfiltrate data piecemeal; establishing an outbound C2 channel through HTTP requests leveraging URL paths.
- First Seen: Assessment performed in 2015.
## MITRE ATT&CK Mapping
- TA0010 - Exfiltration
- T1041 - Exfiltration Over C2 Channel (Implied, using the compromised traffic pathway)
- TA0011 - Command and Control
- T1071 - Application Layer Protocol
- T1071.001 - Web Protocols (Abusing HTTP GET requests)
- TA0005 - Defense Evasion
- T1564.001 - Hide Artifacts: Hidden Files and Directories (Not explicitly detailed for this specific part, but broadly relevant to evasion)
## Functionality
### Core Capabilities
- **Data Exfiltration via URL Path Abuse:** Data (files) is split into small, hex-encoded chunks (e.g., 1500 bytes). Each chunk is appended as a unique path segment in an HTTP GET request to an attacker-controlled server (`http://[ATTACKER SERVER]/[CHUNK_DATA]`).
- **Bypassing DLP:** Because the DLP system (Forcepoint TRITON) attempts to categorize *every* URL path hit, it processes the outbound requests for categorization, allowing the payload (data chunks) to traverse the proxy, even if the subsequent landing site category might ultimately be blocked. The outbound communication is mistaken for legitimate web categorization attempts.
- **Reconstruction:** A simple web server on the attacker side receives these chunks and concatenates them to reconstruct the original file.
### Advanced Features
- **C2 Establishment via Proxy Abuse:** A more advanced script (likely the second one mentioned) was developed to turn the attacker-controlled web server into a functioning C2 server. Internal hosts made requests to the C2 server (e.g., `http://[ATTACKER SERVER]/getchunk`), and the server served back encoded commands.
- **Remote PowerShell Execution:** The C2 capability allowed for remote execution, including invoking external PowerShell scripts hosted on the C2 server root by sending command chunks instructing the local client script to download and execute them (e.g., `Invoke-Script [PS SCRIPT NAME]`). This was further used to perform actions like taking screenshots.
- **Delivery Mechanism:** The initial payload mechanism (likely for establishing the reverse communication channel) was wrapped in a VBA macro, leading to **nine external shells**.
## Indicators of Compromise
*Note: As this focuses on a technique leveraging internal system functions, specific artifacts are primarily related to the attack scripts and delivery.*
- File Hashes: Not specified in the text.
- File Names: `[FILE PATH]` (indicates any file targeted for exfiltration), `Schedule.pdf` (example target).
- Registry Keys: Not applicable.
- Network Indicators: HTTP GET requests utilizing unique URL paths to an external server: `http://[ATTACKER SERVER]/[CHUNK_DATA_HEX]`
- Behavioral Indicators:
- PowerShell instantiating and executing commands via `new-object -com internetexplorer.application`.
- High volume of unique, seemingly random path requests to an external web server originating from an internal host.
- PowerShell executing commands retrieved via HTTP traffic (C2 beaconing).
## Associated Threat Actors
- SensePost Red Team (The group that performed and documented this technique in the context of a 2015 Red Team exercise). *Note: This is not attributed to a known threat group, but rather a penetration testing/red team activity.*
## Detection Methods
- **Signature-based detection:** Not effective against this method, as the activity mimicked legitimate URL categorization requests.
- **Behavioral detection:** The only detection noted was **Carbon Black** observing that PowerShell was executed from within **Microsoft Word** (indicative of macro execution).
- **YARA rules:** Not provided.
## Mitigation Strategies
- **Process Hardening:** Restricting PowerShell execution mechanisms; specifically monitoring for PowerShell being spawned directly from Microsoft Office products (VBA execution).
- **Proxy/DLP Logic Review:** Configuration review of DLP/Web Gateway systems to ensure that requests generated by the system itself (like pre-fetches or categorization attempts) cannot be co-opted for data staging or command delivery.
- **Outbound Traffic Control:** Implementing stricter egress filtering based on destination or content analysis, even for traffic seemingly related to authorized services.
## Related Tools/Techniques
- Exfiltration via DNS tunneling (Similar concept of hiding data in benign-looking protocol requests).
- Use of legitimate applications (like Internet Explorer COM objects in PowerShell) to bypass application allow-listing.