When AI Automations Become Attack Vectors: Are You Aware of the AI Risks in Your Organization?

Streamline your business processes with Microsoft 365 Copilot's new Frontier Agents, enhancing workflow automation for increased productivity. However, have you assessed the risks associated with using it?

Are you aware of the AI tools already in your environment — and what they could do without proper security oversight? With the rapid proliferation of AI-driven automation, tools that once sat quietly in the background are now capable of initiating actions on your behalf — including reading and responding to email. This shift demands intentional thinking about how these tools interact with your systems and expose potential risk.

As enterprises embrace the power of autonomous productivity tools, Microsoft’s Workflow Frontier agents are becoming a central part of how teams automate tasks across Microsoft 365 applications. These agents let users describe what they want in natural language and automatically generate workflows that can interact with Outlook, Teams, SharePoint, Planner, and more — effectively lowering the barrier to automation without requiring any coding.

While tools like Workflow Frontier unlock significant efficiency gains, they also introduce novel attack surfaces: when an agent can act on your behalf, threat actors may find ways to influence or exploit those actions to send unintended replies, disclose sensitive data, or trigger unwanted processes. In this post, we’ll explore how to apply the Threat Modeling Manifesto’s questions-first approach — combined with a threat-hunting mindset — to anticipate and mitigate risks introduced by these AI-driven automations

Here’s a blog-ready version of your Threat Modeling Manifesto assessment — re-formatted into narrative paragraphs with clear sections you can publish as part of your post about Threat Modelling Microsoft Workflow Frontier agents (e.g., automations that reply to email) using a Threat Modeling Manifesto + threat-hunting perspective.

1) What Are We Working On?

This question grounds your understanding of the system.

In this context, Workflow Frontier agents are autonomous automation tools within Microsoft 365 Copilot that perform actions on behalf of users based on natural-language commands. They’re part of Microsoft’s Frontier program, which provides early access to these sophisticated agents and tools like App Builder and Workflows.

These agents operate with identity tokens and scoped permissions to interact across apps and services. Microsoft’s control plane — Agent 365 — provides centralized access control, observability, and governance over agent identities, behaviors, and permissions.

Key risk surfaces to define here include:

• The identity and permission scopes the agent holds;

• Data it can read/write (e.g., mailboxes, calendars, files);

• Triggers that initiate workflows (incoming mail, Teams posts, schedules);

• Downstream effects (automated replies, data writes, notifications).

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A clear map of what the agent touches and the trust boundaries it crosses is the basis for identifying threats.

2) What Can Go Wrong?

Here we shift from passive identification to hypothesis-driven risk exploration — a hallmark of threat hunting.

Because Workflow Frontier agents interpret natural language and take actions dynamically, adversaries may leverage crafted inputs or context manipulations to cause them to misbehave. For example:

• Prompt or input manipulation: Adversaries may construct triggers (e.g., specially formatted emails) that exploit the agent’s interpretation process, leading to unintended replies or actions.

• Credential and permission abuse: Excess permissions — like broad mailbox send rights or cross-app access — can widen the blast radius if those permissions are misused.

• Observation and action injection: Given that agent workflows are built from high-level descriptions, clever attackers could find vectors to introduce malicious logic into the intent that generates the workflow.

  
  

These aren’t theoretical concerns — recent research shows how prompt injection vulnerabilities can be weaponized to exfiltrate data from agent systems. (arXiv) Likewise, real-world phishing campaigns have been reported in the wild where attackers trick Copilot Studio agents into granting OAuth tokens to malicious parties, potentially exposing mail, chat, and file stores. (TechRadar)

This is the moment to ask: How can agent behavior be influenced by an attacker without direct access to its code? That’s a threat-hunting hypothesis you should explore with logs, alerts, and simulations.

3) What Are We Going to Do About It?

After enumerating what can go wrong, the next step is defining both mitigations and hunting strategies.

Governance & Least-Privilege

Assign agents the minimal permissions required to perform their tasks. Agent 365’s control plane and identity/scoping features are designed to limit over-permissioning and enforce Zero Trust principles.

Prompt Sanitization & Validation

Before allowing free-form prompts to generate automation, consider validating inputs against a trusted template or guardrail. In practice, this could mean requiring workflows that send external mail to be reviewed, or disallowing certain classes of actions without explicit approval.

Threat Hunting Playbooks

While a common practice in the cybersecurity industry, threat hunting for AI-related tactics, processes and procedures for AI systems.

It is recommended that dedicated hunts are performed such as:

• Unusual outbound email drafts or replies that weren’t manually initiated;

• Unexpected scope elevation or new permission grants;

• Pattern anomalies around agent triggers and task executions.

These hunts convert your hypotheses from the previous section into measurable detection use cases.

4) Did We Do a Good Enough Job?

Threat modelling is not a one-and-done task.

A critical part of the Threat Modeling Manifesto is iteration — constantly validating and refining your understanding as systems and threats evolve. In the context of Workflow Frontier agents:

• Are telemetry and logs feeding back into new hypotheses?

• Have your hunts turned up anomalous events you hadn’t anticipated?

• As your agents or workflows evolve, has your model been updated?

  
  

Capturing performance and security metrics, trend analyses, and hunt outcomes back into your threat model will keep it relevant. If an agent’s behavior changes — for instance, it begins to automate new classes of tasks — you should revisit its scope and threat assumptions.

Final Takeaway

Workflow Frontier agents offer tremendous automation potential: simplifying tasks traditionally reserved for Power Automate builders or IT admins into natural language workflows. But with that power comes risk — especially when agents can authoritatively respond to email and modify or trigger business processes.

By using the Threat Modeling Manifesto’s questions — not just as a checklist but as active prompts for threat hypotheses and hunting strategies — you gain a dynamic framework for securing these AI-driven automations. Combined with governance, continuous monitoring, and curious threat hunters, you ensure these agents deliver productivity without becoming an exploitable vector in your enterprise.

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