The Tool Desk
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Why securing agents takes more than filtering model output
An agent may read untrusted documents or web content, retain information in memory, act through tools, and use identities with access to business systems. That creates risks beyond harmful text generation: an indirect prompt injection could try to redirect the agent, misuse a tool, expose data, or trigger a consequential action. An agent can also amplify mistakes through repeated or chained actions.
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The OWASP AI Agent Security Cheat Sheet covers risks including direct and indirect prompt injection, tool abuse and privilege escalation, data exfiltration, memory poisoning, goal hijacking, excessive autonomy, high-impact action abuse, approval manipulation, cascading failures, misconfiguration, denial of wallet, sensitive data exposure, and supply-chain attacks. Treat these as a threat map for your environment, not as a list a product can necessarily eliminate.
Use OWASP’s excessive-agency controls to frame the comparison
OWASP’s LLM06:2025 guidance groups excessive agency’s root causes into three areas. Its recommendations are useful whether controls live in an agent-security product, the agent framework, or the downstream application.
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| OWASP concern | What to look for | Buyer question |
|---|---|---|
| Excessive functionality | Keep extensions and available functions to the minimum needed; avoid open-ended extensions where practical. | Can you restrict which tools or functions an agent can call for a given task? |
| Excessive permissions | Use narrow permissions and execute actions in the user’s context where possible. Enforce authorization in downstream systems. | Does the platform reveal which identities and resources an agent can reach, and can it help reduce excessive access? |
| Excessive autonomy | Require human approval for high-impact actions; use monitoring and rate limits to limit impact. | Can a policy stop an action before execution and require an independent approval? |
Monitoring and rate limits can reduce the impact of excessive agency, but OWASP does not treat them as substitutes for preventing it. Likewise, authenticating an agent message is not the same as authorizing its requested operation. OWASP’s Cheat Sheet states: “A valid message signature does not grant permission to perform the requested action.”
Compare enforcement points, not product labels
Map each protection to the moment it can act. A product may inspect one event type but not another, or alert on activity without blocking it. Ask for the exact event, decision, and outcome supported in each environment.
Rank #2
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- FAST & CONVENIENT LOGIN: Plug in your YubiKey 5 NFC via USB and tap it, or tap it against your phone (NFC), to authenticate. No batteries, no internet connection, and no extra fees required
- MOST SECURE PASSKEY: Supports FIDO2/WebAuthn, FIDO U2F, Yubico OTP, OATH-TOTP/HOTP, Smart card (PIV), and OpenPGP. That means it’s versatile, working almost anywhere you need it
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| Enforcement point | Protection to verify | Evidence to request |
|---|---|---|
| Prompt or input | Inspection of user prompts and untrusted content the agent ingests, including indirect injection attempts. | Which input sources are inspected? Can a policy block, modify, or only flag a suspicious instruction? |
| Before a tool call | Policy evaluation of the requested tool, arguments, identity, and intended action before execution. | Show an unsafe call being denied before it reaches the tool. Can the policy distinguish read from write operations? |
| Tool response | Inspection of returned content for malicious instructions, sensitive data, or unexpected results before the agent uses it. | Which response paths are covered, and can the platform prevent the agent from acting on a flagged response? |
| Downstream authorization | Permissions are enforced by the system that owns the data or action, not just by the model’s interpretation of policy. | Does the agent act as the user or through a broad service identity? Where is authorization ultimately enforced? |
| High-impact action | An approval gate for actions such as deleting data, sending external communications, or initiating financial operations. | Can approval be required before execution, and is the approver independent of the agent’s decision? |
| After an event | Auditable logs, alerts, and investigation support. | What is recorded, how is it tied to the agent and identity, and can responders trace the full action sequence? |
What the documented Microsoft and Palo Alto capabilities cover
The following is a comparison of capabilities described in the cited vendor materials, not a head-to-head test. The products describe different scopes, and a feature being documented does not independently establish its effectiveness.
| Area | Microsoft Defender | Palo Alto Networks Prisma AIRS |
|---|---|---|
| Discovery and inventory | Microsoft documents local AI-agent discovery on onboarded endpoints, a central inventory, device and user associations, an exposure map linking agents to identities and resources reachable by those identities, and advanced hunting. Source: Microsoft Defender documentation on AI agent discovery. | The product page describes discovery across SaaS, cloud, low-code, and custom environments. A March 23, 2026 announcement also described discovery across cloud, SaaS, and endpoint environments. Sources: Prisma AIRS product page; Palo Alto Networks announcement. |
| Prompt, tool-call, and response inspection | Endpoint runtime protection is documented to inspect prompts, pre-tool requests, and post-tool responses through agent-native event interfaces where supported. Microsoft says it can audit or block activity at supported event points. Source: Microsoft Defender endpoint runtime protection documentation. | The product page describes runtime security against prompt injection and tool misuse. The specific inspection events, enforcement behavior, and coverage by framework are not established in the cited material here. Source: Prisma AIRS product page. |
| Identity and access | The documented exposure map connects agents to identities and resources those identities can reach. Whether a specific excessive permission can be remediated through the product is not stated in the cited material. Source: Microsoft Defender AI agent discovery documentation. | The product page describes identifying excessive access and validating agent identities. The enforcement mechanisms and downstream authorization behavior are not stated in the cited material. Source: Prisma AIRS product page. |
| Pre-deployment and supply chain | Code, MCP server, skill, or plugin scanning is not stated in the Microsoft endpoint materials summarized here. | The product page describes scanning agent artifacts including code, MCP servers, and skills. The specific remediation workflow is not stated in the cited material. Source: Prisma AIRS product page. |
| Testing and evaluation | Adversarial behavior testing or task-specific test coverage is not stated in the Microsoft materials summarized here. | The product page describes behavior testing with attack libraries or dynamic red teaming. The cited material does not establish independent results or a common benchmark against other platforms. Source: Prisma AIRS product page. |
| Release status and constraints | The endpoint runtime protection documentation labels the capability Preview. Microsoft lists Claude Code, Codex CLI, GitHub Copilot CLI, and GitHub Copilot app for agent-native inspection, and describes network inspection for some agents without event interfaces. Network inspection does not support certificate-pinned or HTTP/3 agents. Source: Microsoft Defender endpoint runtime protection documentation. | Palo Alto’s March 23, 2026 announcement described the AI Agent Gateway as in limited preview at that time. The current release status is not established by that dated announcement. Sources: Palo Alto Networks March 23, 2026 announcement; Prisma AIRS product page. |
These descriptions should not be read as a scorecard: a blank or “not stated” cell means the cited material does not establish that detail, not that the vendor lacks the capability. Microsoft’s cloud-agent threat detection is a separate area from the endpoint runtime blocking described above; do not assume that one proves the other is available or works the same way.
Rank #3
- POWERFUL SECURITY KEY: The YubiKey 5C NFC is the most versatile physical passkey, protecting your digital life from phishing attacks. It ensures only you can access your accounts
- WORKS WITH 1000+ ACCOUNTS: Compatible with popular accounts like Google, Microsoft, and Apple. A single YubiKey 5C NFC secures 100+ of your favorite accounts, including email, password managers, and more
- FAST & CONVENIENT LOGIN: Plug in your YubiKey 5C NFC via USB and tap it, or tap it against your phone (NFC), to authenticate. No batteries, no internet connection, and no extra fees required
- MOST SECURE PASSKEY: Supports FIDO2/WebAuthn, FIDO U2F, Yubico OTP, OATH-TOTP/HOTP, Smart card (PIV), and OpenPGP. That means it’s versatile, working almost anywhere you need it
- PRIMARY & SPARE KEYS: Just like having a spare house key, we recommend buying two YubiKeys - one for daily use and one as a spare. That way you’ll never get locked out of your accounts
How to evaluate a platform against your agents
- Inventory the estate. List cloud, SaaS, low-code, custom, and endpoint agents, along with owners, frameworks, identities, connectors, tools, and reachable resources. Check whether discovery depends on onboarding devices or adding specific integrations.
- Trace a real task end to end. For a representative workflow, identify every prompt and untrusted input, tool request, tool response, identity, downstream system, and high-impact action. Mark where a platform can inspect, block, require approval, or only log.
- Run task-specific adversarial scenarios. Include indirect prompt injection in documents or other ingested content, tool misuse, attempts to exfiltrate data, and attempts to bypass approval. Use workflows and data boundaries that resemble your own rather than relying only on a generic attack demo.
- Repeat tests and inspect outcomes. Test repeated attempts, variations in attack wording, and actions chained across tools. Record task-level outcomes as well as aggregate results, and distinguish blocked actions from alerts raised after execution.
- Check permissions and recovery. Verify the identity used for each action, the downstream system’s authorization decision, what an approver sees, and how an incident responder can trace or contain activity.
- Confirm deployment fit and operating terms. Ask which frameworks, protocols, endpoints, cloud providers, and network paths are covered; what instrumentation, connectors, endpoint agents, or network placement are required; what data is logged or sent; and what licensing and regional availability apply.
Why repeatable, adaptive testing matters
NIST’s Center for AI Standards and Innovation (CAISI) describes agent hijacking as indirect prompt injection: malicious instructions embedded in ingested data cause unintended actions. In a particular evaluation using AgentDojo environments and additional attacks, a new red-team attack raised measured attack success from 11% for the strongest baseline attack to 81% on held-out Workspace tasks. In a separate result across five injection tasks, repeating each attack 25 times raised average attack success from 57% to 80%. These are results from those specific setups, not universal rates for deployed agents or a benchmark of security platforms. The publication was released January 17, 2025 and updated December 19, 2025.
The practical lesson is to ask whether vendor tests adapt attacks to the target system, measure whether the task-level outcome was actually achieved, and account for retries. NIST’s AI Agent Standards Initiative page, created February 17, 2026 and updated August 14, 2026, says NIST is researching agent authentication and identity infrastructure and developing security evaluations for protocol development and consumer comparison. That work is relevant context, not evidence that vendors have already been evaluated on a common standard.
Rank #4
- POWERFUL SECURITY KEY: The Security Key NFC is the essential physical passkey for protecting your digital life from phishing attacks. It ensures only you can access your accounts.
- WORKS WITH 1000+ ACCOUNTS: Compatible with Google, Microsoft, and Apple. A single Security Key NFC secures 100 of your favorite accounts, including email, password managers, and more.
- FAST & CONVENIENT LOGIN: Plug in your Security Key NFC via USB-A and tap it, or tap it against your phone (NFC) to authenticate. No batteries, no internet connection, and no extra fees required.
- TRUSTED PASSKEY TECHNOLOGY: Uses the latest passkey standards (FIDO2/WebAuthn & FIDO U2F) but does not support One-Time Passwords. For complex needs, check out the YubiKey 5 Series.
- BUILT TO LAST: Made from tough, waterproof, and crush-resistant materials. Manufactured in Sweden and programmed in the USA with the highest security standards.
Availability, coverage, and evidence to verify
Release status can change, and a preview feature may have different support or operating conditions from a generally available one. Microsoft’s endpoint runtime protection documentation marks the capability Preview. Palo Alto’s March 23, 2026 announcement said the AI Agent Gateway was in limited preview at that time. Ask vendors for the current status in your region and edition, the supported agent versions and integrations, and any limitations that apply to the specific enforcement points you need.
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsOWASP’s Q3 2025 AI Security Solutions Landscape maps open-source and commercial solutions across the agentic lifecycle and says it is peer-reviewed and updated quarterly. Use it to understand the market, not as a product test or endorsement. The vendor materials compared here do not establish like-for-like pricing, independently verified feature performance, or a single best platform. Confirm current licensing, data handling, regional availability, auditability, and incident-response integration directly with each vendor.
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