Running a phishing simulation against a third-party vendor is different from testing your own staff — you don't control their inbox policies, their reporting culture, or their tolerance for being tested. Get the setup wrong in 2026 and you burn the relationship before you get useful data.
TL;DR
- Phishing simulation third party vendors programs need signed consent, isolated tracking, and a clear escalation rule before launch.
- Cyber Aware recommends piloting with one vendor cohort before rolling simulations across the full vendor register.
- A vendor click rate above 15% on a first simulation signals a contract review, not just more training.
- Never impersonate the vendor's own brand or executives without written legal sign-off from both sides.
Why this matters
Third-party vendors are the entry point for a growing share of breaches reported to the OAIC under Australia's Notifiable Data Breaches scheme, and most vendor contracts still don't require phishing testing as a condition of access. If a vendor's staff can click their way into your systems, your own security awareness training budget is irrelevant.
Regulators are catching up. APRA CPS 234 and the SOCI Act both push accountable entities to demonstrate oversight of third-party cyber risk, not just their own. A documented phishing simulation program against vendors is one of the cleanest ways to show an auditor you're managing that exposure rather than assuming it away.
What you'll need
- Written consent from the vendor — a simulation without sign-off is indistinguishable from a real attack and can trigger a genuine incident response on their end
- A vendor contact list segmented by system access level — not every vendor employee needs testing, only the ones with credentials into your environment
- A phishing simulation platform that supports external domains — most platforms are built for internal staff and need configuration for vendor-owned email domains
- A baseline click-rate target agreed with the vendor before the first send, so results aren't a surprise
- An escalation contact on the vendor side who isn't the person being tested
- 3-4 weeks lead time — vendor legal and procurement teams move slower than internal comms
If the vendor relationship involves contractors rather than full-time staff, review the approach for training contractors on security awareness first — the consent and reporting lines differ from a standard employee cohort.
The steps
1. Get consent in writing before you build anything
A verbal nod from your vendor contact is not enough. Draft a one-page addendum that names the simulation window, the template categories you'll use, and what happens with the results — who sees the click data and whether it affects the contract.
Skipping this step is the single most common reason vendor phishing programs get shut down after one round. Common mistake: sending the simulation to a vendor's shared support inbox instead of named individuals, which triggers a real security team response and burns trust immediately.
2. Segment vendors by access tier, not by size
A five-person bookkeeping vendor with access to your payment system carries more risk than a 200-person marketing agency with none. Rank vendors by what systems and data they can touch, then test the high-access tier first.
This mirrors how internal programs approach segmenting phishing simulations by department risk — finance and IT-adjacent roles get tested more often than low-risk departments. Apply the same logic across your vendor register instead of your org chart.
3. Pilot with one vendor before scaling
Run the first simulation against a single cooperative vendor, not your entire supply chain at once. A pilot exposes formatting problems — external email banners that make your fake phishing email obviously fake, spam filters on the vendor's end that block the send entirely, or reply-to addresses that route to the wrong inbox.
Expected outcome: a working template and delivery process you can replicate. If the pilot vendor's click rate comes back under 5%, treat that as a benchmark, not a target — vendors with less internal training exposure typically run higher on a first attempt.
4. Use realistic but low-harm templates
Build simulations around invoice changes, calendar invites, and software renewal notices — categories vendors actually receive from real partners. Avoid impersonating the vendor's own executives or brand without separate written approval; that crosses from testing into reputational risk if it leaks internally.
Common mistake: reusing an internal staff template word-for-word. Vendor staff don't recognize your internal tools or jargon, so the pretext falls flat and the data becomes unreliable.
5. Track results outside the vendor's own systems
Don't rely on the vendor to self-report click data — it introduces bias and delay. Route tracking through your own simulation platform so click timestamps, credential-entry attempts, and reporting behavior all land in one place you control.
This is also where the exercise stops being a one-off test and starts feeding vendor risk management using training data — click history becomes a factor in renewal and access-tier decisions, not just a training metric.
6. Set a response window before you send
Agree on 48-72 hours as the reporting window and tell the vendor contact what "pass" and "fail" mean in numeric terms before launch — for example, under 10% click rate and at least one staff report within the window. Ambiguous scoring is the fastest way to get a result disputed after the fact.
7. Debrief with data, not blame
Share the click rate, the report rate, and the time-to-report with the vendor's management contact within a week. Frame repeat failures as a contract and access conversation, not a personal one aimed at individual staff.
Expected outcome: vendors with clean results get lighter-touch testing going forward; vendors with repeat high click rates move to quarterly testing or a documented remediation plan.
Set up vendor phishing testing
See how Cyber Aware handles multi-tenant simulation tracking across vendor and staff cohorts.
Troubleshooting
- Vendor's spam filter blocks the simulation entirely — request a temporary allowlist entry for the sending domain, scoped only to the test window
- Vendor disputes the click-rate result — pull raw timestamp logs from your platform rather than relying on the vendor's own screenshots
- Staff report the simulation to their own IT team as a real incident — build a heads-up note to the vendor's IT lead (not general staff) so they don't waste time on incident response for a test
- Click rate comes back suspiciously low (under 2%) — check whether the vendor forwarded a warning to staff before the test ran; this invalidates the baseline and the round should be rerun in 2026's next quarter cycle
- Vendor pushes back on any testing at all — cite the contract clause or, if none exists, propose adding one at the next renewal rather than forcing an unwilling test
- Repeat high click rates from the same vendor — this is a contract and access-tier conversation, covered in the escalation path for repeat clickers, adapted for external parties rather than internal staff
Tools and resources
- A phishing simulation platform that supports sending to external domains and tracking outside your own tenant
- A written vendor consent addendum template, reused across every new vendor test
- A shared tracker mapping vendor name, access tier, last test date, and click rate
- Regulatory references worth keeping on hand: APRA CPS 234, the SOCI Act, and the Notifiable Data Breaches scheme guidance from the OAIC
What to do next
Once vendor testing is running on a cycle, the next problem is usually proving it's working to whoever asked for it — a board, an auditor, or a client demanding evidence of oversight. That's a separate exercise from running the test itself and worth planning for before your first annual review.
FAQ
How often should you run phishing simulations on third-party vendors?
High-access vendors should be tested quarterly in 2026; low-access vendors can be tested twice a year. Frequency should scale with what systems and data the vendor can reach, not with vendor headcount.
Do you need vendor consent before running a phishing simulation on their staff?
Yes, written consent is required before any vendor phishing simulation. Without it, the test can trigger a real incident response on the vendor's side and creates legal exposure for both parties.
What's a reasonable phishing click rate for a vendor's first simulation?
A first-round click rate under 10% is a reasonable pass threshold, though vendors with no prior training exposure often score higher. Treat the first test as a baseline, not a judgment.
Should vendor phishing results affect the contract?
Repeat high click rates should trigger an access-tier review or remediation plan written into the vendor agreement. A single bad result is a training gap; a pattern is a contract issue.
Can you use the same phishing templates for vendors and internal staff?
No, vendor templates need different pretexts since vendor staff don't recognize internal tools, systems, or jargon. Invoice changes and software renewal notices generally work better for external audiences than internal-style prompts.
Who should see vendor phishing simulation results?
The vendor's management contact and your own vendor risk owner, not the individual staff who clicked. Naming individuals externally damages the relationship without improving the outcome.
What happens if a vendor refuses phishing testing?
Without a contract clause requiring it, you can't force testing, but you can flag the gap for the next renewal cycle. Document the refusal as part of your vendor risk record for audit purposes.
One last thing
The vendors that resist testing hardest are usually the ones with the least internal security awareness training already in place — that resistance is itself a data point. Log it alongside click rates when you build the vendor risk picture.