Cobalt Strike 413's Custom Watermark: Red Teaming's New Branding Frontier + Video

Introduction:

Cobalt Strike 4.13, released on June 10, 2026, under the codename “Lost in Translation,” introduces a wealth of new features, including C scripting via the Beacon Interpreter, BOF-PE (Beacon Object File – Portable Executable) support, and significant REST API enhancements. Among these updates lies a seemingly minor but critically important quality-of-life improvement: the ability to customize the UI watermark image within the Beacon console. For red teamers and security practitioners, this feature represents more than just aesthetic personalization—it’s a powerful tool for client engagement, operational branding, and professional presentation during adversarial simulations.

Learning Objectives:

Understand the technical implementation and security implications of Cobalt Strike’s watermarking system.
Master the Aggressor Script commands to customize and reset the Beacon console watermark image.
Learn to leverage Malleable C2 Profile overrides for dynamic payload generation.
Develop skills to extract and analyze watermark artifacts for threat intelligence and attribution.
Implement operational security best practices when using watermarked Cobalt Strike instances.

Understanding Cobalt Strike Watermarks: From License Fingerprint to Visual Branding

Cobalt Strike’s watermarking system has long served as a critical license fingerprinting mechanism. At its core, a watermark is a unique 4-byte integer tied to the `CobaltStrike.auth` file, essentially acting as a license identifier. This watermark is embedded within every generated Beacon payload and can be extracted using most Beacon configuration parsers. Matching watermarks across different beacons can indicate the use of the same Cobalt Strike license—though not necessarily the same operator, as licenses and auth files are often shared or pirated.

From a defensive perspective, watermark values provide invaluable threat intelligence for attribution. Security researchers have linked specific watermark values to particular threat actors or campaigns; for example, watermark “391144938” has been associated with activities in the Asian gambling sector. Watermarks have also been used to correlate attacks with the Black Basta ransomware group, as unique beacon watermarks were identified in campaigns linked to Initial Access Brokers (IABs) associated with that threat actor.

With Cobalt Strike 4.13, the watermark concept expands beyond license fingerprinting into the user interface realm. The new `beacon_console_watermark` and `beacon_console_watermark_reset` Aggressor commands allow operators to display a custom image as a watermark within the Beacon console. This enhancement enables red teams to brand their operations with client logos, engagement identifiers, or internal team markings—creating a more professional and accountable testing environment.

2. Implementing Custom Watermarks with Aggressor Script

The custom watermark functionality in Cobalt Strike 4.13 is accessed through Aggressor Script, the built-in scripting language that extends the Cobalt Strike client. The two primary commands are:

beacon_console_watermark(<image_path>): Sets a custom watermark image for the Beacon console.
beacon_console_watermark_reset(): Resets the watermark to the default Cobalt Strike branding.

Step-by-Step Guide to Implementing Custom Watermarks:

Prepare Your Image: Create or select an image file suitable for use as a watermark. While specific dimension requirements aren’t explicitly documented for the console watermark, best practices suggest using a PNG file with transparency support for optimal visual integration. The reporting engine previously required images at 1192x257px at 300dpi for report logos, serving as a reasonable reference point.
Load Your Aggressor Script: Open the Cobalt Strike client, navigate to Cobalt Strike -> Script Manager, and click “Load” to load your `.cna` script file. Alternatively, you can execute commands directly from the Script Console.
Set the Watermark: In the Script Console or within your Aggressor Script, execute:
```
beacon_console_watermark("/path/to/your/watermark.png");
```
This command applies the custom watermark to all active Beacon consoles.
Reset to Default: To remove the custom watermark and revert to the default Cobalt Strike branding, use:
```
beacon_console_watermark_reset();
```
Automate with Scripts: For persistent branding across operations, incorporate these commands into your initialization scripts:
```
on beacon_initial {
beacon_console_watermark("/opt/cobaltstrike/branding/client_logo.png");
}
```
Leveraging Malleable C2 Profile Overrides for Dynamic Payload Generation

Cobalt Strike 4.13 introduces Malleable Profile Overrides, allowing operators to dynamically change certain settings as new payloads are generated without restarting the Team Server. This feature complements the watermark functionality by enabling per-engagement or per-client customization.

Supported Override Settings:

useragent: Custom User-Agent strings for HTTP/HTTPS communication
checkin_delay: Adjustable sleep intervals between beacon check-ins
stage.: All fields in the stage group
process-inject.: All fields in the process-inject group

Step-by-Step Guide to Using Malleable Profile Overrides:

Create an .mpo File: Open the Malleable Profile Override dialog from any payload generation dialog (Stageless Payload Generator, Windows Stageless Payload, etc.). Create a new `.mpo` file with your desired overrides.

Define Overrides: Use syntax matching the existing Malleable C2 Profile configuration. For example:

set useragent "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36";
set checkin_delay "60000";
set stage {
set cleanup "true";
}

Validate and Save: Use the Verify button to confirm syntax validity, then save your `.mpo` file. Files are stored in an application-specific folder under the operating system user’s data folder.
Generate Payloads: When generating payloads through GUI dialogs, Aggressor commands (artifact_payload, all_payloads, payload), or the REST API endpoint (/api/v1/payloads/generate/stageless), select your `.mpo` file from the override list.
Use Ad Hoc Changes: Unsaved changes can be used to generate the current payload without saving the file—indicated by “(edited)” next to the file name.

4. Operational Security and Watermark Forensics

The ability to customize console watermarks introduces important operational security considerations. While visual branding enhances professionalism, red teamers must remain aware that watermarks remain embedded in payloads and can be extracted by defenders.

Extracting Watermarks for Threat Intelligence:

From a defensive perspective, extracting watermark values from captured beacons enables threat hunting and attribution. Common tools and techniques include:

Beacon Configuration Parsers: Tools like `beacon_parser` and `cs-extractor` can parse the Beacon configuration and extract the 4-byte watermark integer.
Shodan Queries: Security researchers can identify Cobalt Strike beacons through Shodan using specific fingerprints, correlating watermarks with infrastructure.
PowerShell Analysis: Custom PowerShell scripts can be developed to extract and analyze watermark patterns from network traffic.

Linux Command Example – Extracting Watermark from Beacon Payload:

 Using a beacon configuration parser (hypothetical example)
python3 beacon_extractor.py -f beacon.exe --show-watermark
 Output: Watermark: 391144938 (0x1750B9EA)

Windows Command Example – Analyzing Captured Traffic:

 Extract watermark from PCAP using tshark and custom parsing
tshark -r capture.pcap -Y "http.request.uri contains '/beacon'" -T fields -e data | 
ForEach-Object { [System.Text.Encoding]::UTF8.GetString([System.Convert]::FromBase64String($_)) } | 
Select-String -Pattern "watermark"

API Security and Automation with Cobalt Strike 4.13

The REST API, introduced in version 4.12, continues to evolve in 4.13 with enhanced functionality for automated operations. The API now supports WebSocket and gRPC streams, improved error handling (HTTP 401 for password errors), and full user name inclusion in logging.

REST API Endpoints for Payload Generation:

POST /api/v1/payloads/generate/stageless: Generate stageless payloads with Malleable Profile overrides
BOF-PE endpoints for executing EXE and DLL binaries directly in Beacon
Beacon Interpreter endpoints for C scripting integration

API Security Best Practices:

Token Management: Secure your REST API tokens and rotate them regularly. The improved token-store steal endpoint documentation helps operators understand and mitigate token theft risks.
Logging and Monitoring: With full user names now included in REST API logging, implement robust monitoring to detect unauthorized API access.
Credential Handling: The password attribute has been removed from REST API credential endpoints, replaced with `secret` for improved security.

Linux Command – Interacting with Cobalt Strike REST API:

 Generate a stageless payload with Malleable Profile Override
curl -X POST https://teamserver:8443/api/v1/payloads/generate/stageless \
-H "Authorization: Bearer YOUR_API_TOKEN" \
-H "Content-Type: application/json" \
-d '{
"listener": "https-listener",
"output": "exe",
"override": "engagement_client.mpo"
}'

6. Advanced Beacon Operations in 4.13

Cobalt Strike 4.13 introduces several enhancements to Beacon operations that complement the watermark functionality:

Beacon Interpreter: C scripting directly in Beacon, enabling complex automation and custom logic
BOF-PE Support: Run both EXE and DLL binaries in Beacon, expanding post-exploitation capabilities
BEACON_INLINE_EXECUTE Hook: Intercept and modify BOFs before execution, enabling modular automation
Drip-Loading: Improved memory allocation and process injection techniques
Sleepmask Enhancements: Return address spoofing and increased size limits (100 MB)
Payload Store: Export and share artifacts and metadata on the Team Server

Step-by-Step Guide – Deploying a BOF-PE Payload:

Generate Payload: Use the Stageless Payload Generator or REST API to create a BOF-PE payload.
Execute in Beacon: From the Beacon console, use the appropriate command to execute the BOF-PE:
```
bofpe /path/to/payload.exe
```
Monitor Output: The Beacon console displays output and task completion status, enhanced with improved task state tracking in 4.13.

What Undercode Say:

Watermarks Are Dual-Use: The ability to customize console watermarks serves both professional branding and operational security. Red teams can now present polished, client-specific interfaces while maintaining the underlying license watermark for attribution tracking.
Automation Is the Future: With Malleable Profile Overrides and the REST API, Cobalt Strike 4.13 enables unprecedented automation in payload generation. Teams can now dynamically adjust C2 profiles per engagement without restarting infrastructure—a game-changer for large-scale operations.
Defenders Must Adapt: The evolution of Cobalt Strike’s watermarking and obfuscation capabilities means defenders must continuously update their detection methodologies. Static signatures are insufficient; behavioral analysis and traffic pattern recognition are essential.
Training and Skill Development: The complexity of features like BOF-PE, Beacon Interpreter, and custom Aggressor scripting underscores the importance of formal training. Courses like those offered by Zero-Point Security (BOF Development & Tradecraft, UDRL and Sleepmask Development) are becoming increasingly valuable for red team practitioners.

The 4.13 release represents a significant leap forward in offensive security tooling. The watermark customization feature, while seemingly cosmetic, reflects a broader trend toward professionalization in red teaming—where presentation, automation, and client engagement are as important as technical capability. For defenders, the proliferation of customizable C2 frameworks demands more sophisticated threat hunting approaches that go beyond simple signature matching.

Prediction:

+1 The customization and automation features in Cobalt Strike 4.13 will accelerate the adoption of professional red teaming services, as engagement teams can now deliver more polished, client-specific experiences without sacrificing operational efficiency.
+1 The Beacon Interpreter and BOF-PE capabilities will drive innovation in offensive security tooling, enabling faster development cycles and more creative attack techniques that benefit the broader security community through improved defensive testing.
-1 The enhanced obfuscation and customization options will be rapidly adopted by threat actors, making detection and attribution more challenging for defenders. Watermark-based threat intelligence will require more sophisticated correlation techniques.
-1 As Cobalt Strike becomes more automated and API-driven, the barrier to entry for malicious actors will decrease, potentially leading to an increase in commodity ransomware and cybercrime operations leveraging these advanced features.
+1 The improved REST API and automation capabilities will enable better integration with Security Orchestration, Automation, and Response (SOAR) platforms, allowing blue teams to simulate attacks more effectively and test defenses at scale.

▶️ Related Video (88% Match):

https://www.youtube.com/watch?v=0qJLKcOrIyQ

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