Third-party vendors sit inside your attack surface even when they never log in to your office. This guide shows how to run phishing simulations for third-party vendors without collecting credentials, damaging supplier trust, or turning a useful test into a contractual dispute. Start with a phishing simulation programme and make the exercise one part of a documented vendor-risk process.
TL;DR
- Get written authority before testing a supplier, and define who owns the exercise, the data and the follow-up.
- Start with three vendor cohorts: payment-facing suppliers, privileged service providers and lower-risk operational vendors.
- Use safe simulations that record delivery, clicks and reports but never collect real passwords or trigger a real payment action.
- Give every participant a short coaching moment within 24 hours, then assign deeper training to repeat failures.
- Compare report rate, time to report and verification behaviour alongside click rate.
- Re-run a comparable scenario after 30 to 60 days before declaring the programme effective in 2026.
Why this matters
A supplier can send mail from a trusted domain, manage a cloud service, approve an invoice or hold a support credential. That makes a vendor impersonation email more dangerous than a generic test sent to an internal mailbox. The employee who receives it may be trying to keep a project moving, not make a security decision, which is exactly the pressure an attacker exploits.
The Australian Signals Directorate’s supply-chain guidance says organisations should identify suppliers, understand the risk they introduce, set expectations, check whether those expectations are met, and keep improving. A phishing simulation is useful when it tests one of those decisions. It is wasteful when it is just a scorecard of who clicked.
ASD’s Annual Cyber Threat Report 2024–25 recorded phishing in 60% of incidents reported to the Australian Cyber Security Centre. That number does not mean every vendor test should imitate a live attack. It does mean the human response to a suspicious supplier message deserves a place in the vendor-risk plan for 2026.
Step 1: define the decision you want to test
Do not begin with a template. Begin with a decision. Decide whether the exercise is testing a bank-detail change, a supplier portal sign-in, a new support contact, an urgent remote-access request or a document shared by a known vendor. Each one has a different safe response.
Write the expected action in one sentence: pause the request, use the approved contact record, verify the change out of band, and report the message. Give that sentence to the service owner and help desk before the campaign starts.
The goal is to measure one defined behaviour: pause, verify through a known channel, or report. Choose one decision for the first campaign and keep the learner action to three steps or fewer.
Step 2: confirm authority and guardrails
Vendor testing needs more than an internal go-ahead. Check the master services agreement, security schedule, acceptable-use rules and any notification obligations. Identify whether the vendor, the client, or both must approve the test. Put the decision in writing.
Set the boundaries before content is built. Do not use a real executive approval, a live bank account, an active password reset or a message that could cause a supplier to stop service. Do not test a vendor’s staff outside the agreed audience.
The guardrail is simple: obtain written approval, list the sending and landing-page domains, and name someone who can stop the campaign. Give the vendor a clear answer if it asks whether the message was authorised.
Step 3: build useful cohorts
Group people by the decisions they make, not only by the supplier’s name. Payment and procurement teams need bank-detail and invoice scenarios. Technical service providers need access, support and privileged-account scenarios. General suppliers need document-sharing, delivery and account-verification scenarios.
Keep each cohort small enough to explain. A first campaign with 20 to 50 people gives the owner a manageable debrief and makes it easier to spot a broken reporting route. Larger campaigns can follow once the process works.
Create three cohorts, assign a service owner to each, and record the business process, access level and verification route. Keep vendor and internal results separate because their contracts and reporting obligations differ.
Step 4: design a safe simulation
Use a believable but non-operational scenario. A simulated supplier can ask the recipient to review a new service notice, confirm a meeting document or call a known contact about a change. Do not copy a real invoice number, bank account, customer name or current incident.
Use a landing page that explains the exercise immediately after a click. It should show two or three clues, state the correct next step and provide the real reporting route. The page should not ask for a password, a one-time code, a payment reference or personal information.
The landing page should explain the exercise immediately, show two or three clues and give the reporting route. Never collect passwords, one-time codes, payment details or personal information; the objective is a pause-and-verify habit, not a higher click rate.
Step 5: launch in a controlled window
Send the first message during a period when the service owner, help desk and security contact are available. Stagger delivery by cohort if vendors operate across time zones. Keep the first campaign short enough to investigate unusual reports before sending another message.
Track delivery, opens where available, clicks, reports, time to report, visits to the coaching page and requests for clarification. Treat a report as a positive signal even when the recipient did not know whether the message was simulated.
Monitor the first 4 hours, review the first 24 hours and close after 72 hours unless the approved plan says otherwise. Delivery, reporting and time-to-report data must be read separately from learner judgement.
Step 6: coach, remediate and protect trust
Give every participant the same respectful explanation. Show the message, identify the pressure cue, explain the verification route and state that reporting was the desired action. Never publish a list of people who clicked.
For repeat failures, assign a focused lesson and a manager conversation rather than increasing the embarrassment. Cyber Aware’s security awareness training page describes story-driven lessons, quizzes and completion tracking that can support this kind of follow-up when the vendor and client agree on the delivery model.
Send coaching within 24 hours, assign focused remediation to repeat failures and review overdue work at 7 days. Keep individual results restricted; people must feel safe reporting the next suspicious request.
Step 7: compare and repeat
Review the result with the vendor owner and the process owner. Compare the same cohort, scenario type and reporting route where possible. Use click rate as one signal, but give equal attention to report rate, verification rate, time to report and the number of people who asked for help.
Run a comparable follow-up after 30 to 60 days. Change one variable at a time: the sender identity, the urgency, the document type or the delivery channel. If every variable changes, you cannot tell whether behaviour improved or the message simply became easier.
Set a 30-day process review, a 60-day comparable test and a 90-day decision on cadence and scope. Change one variable at a time and report an owned action, not just a percentage.
Troubleshooting
The vendor says the simulation was unauthorised
Stop, preserve the message and let the contract owner explain the scope. Restart only after written approval is confirmed.
The message triggers real payment work
Stop immediately and contact finance through the known route. Record the near miss separately; never use a real account or invoice in a simulation.
Nobody reports the message
Check the reporting route, run a report-only exercise and repeat the scenario. A broken route is not a learner failure.
Tools and resources
- Use human risk reporting to bring completion, quiz and phishing behaviour into one view when the client’s data-handling rules allow it.
- Use a cyber security gap assessment to map suppliers, processes and ownership before expanding the simulation programme.
- Review the ASD guidance on managing cyber supply chains for the wider supplier-risk process.
- Read the ASD Annual Cyber Threat Report 2024–25 for current Australian threat context.
FAQ
Should you run phishing simulations against third-party vendors?
Yes, when the vendor, contract owner and data owner authorise the exercise in writing. The simulation should test a defined supplier decision, avoid credential collection and include a clear coaching and reporting process.
What is a good first vendor phishing scenario?
A changed supplier contact or document-review request is a practical first scenario because it tests pause, known-channel verification and reporting without imitating a real payment instruction.
How should vendor simulation results be reported?
Report by cohort, process, campaign date and service owner. Include delivery, click, report, verification and time-to-report measures, and keep individual results restricted to people who need them for remediation.
One last thing
The strongest vendor simulation is the one that makes the safe response easier than the unsafe one. If the approved callback number is buried in an old spreadsheet and the suspicious email sits in front of the buyer, training alone will not fix the gap. Repair the process, then test the behaviour again in 2026.
What to do next
Use the Cyber Aware comparison page to frame platform questions around phishing workflows, reporting, multi-tenant delivery and evidence. Then write the first scenario, approval owner and reporting route into the vendor-risk plan before selecting a cadence.
Related guides
Sources
- Managing cyber supply chains, ASD’s Australian Cyber Security Centre guidance, accessed August 2026.
- Annual Cyber Threat Report 2024–2025, ASD’s ACSC report covering FY2024–25, published 14 October 2025.