To map data flowing to third parties, list each service, each external vendor it calls, and the data classes sent on each connection. Draw services on the left, vendors on the right, and label every line with the data class and direction. One page is enough to start.
Why a map beats a list
An inventory row says "Service A uses Vendor X." A map shows that Vendors X and Y both receive email addresses from Service A, and that Vendor Z receives order history from three services. Patterns like that stay hidden in a long table.
OWASP stresses that sensitive data flows to third parties need visibility, approval and knowledge of the exact data types shared, and says this inventory plays an important role in an incident response plan when a breach happens on the third party side. A map is the quickest way to see that at a glance.
Steps
- Pick the data classes. Keep to four or five, such as public, internal, personal, payment and credentials. Define each in one line.
- Take the integration rows. Use your inventory as the source, one connection per row.
- Place nodes. Your services in a column, vendors in another. Group vendors by purpose: payments, email, analytics, identity, storage.
- Draw edges with labels. Each line gets a direction and the highest data class that crosses it. Use a different line style for inbound webhooks.
- Mark gaps. Use a dashed line for any flow you suspect but cannot confirm, and assign someone to check.
- Date it and store it. Keep the file beside the inventory and update it when rows change.
What to look for on the finished map
| Pattern | What to ask |
|---|---|
| A vendor receiving personal data from many services | Is that consolidated on purpose? |
| A vendor with a high data class and no named owner | Who approved this? |
| Analytics or logging vendors receiving payment or credential data | Is data masked before it leaves? |
| Vendors receiving production data from staging | Should this use a sandbox? |
| One service fanning out to many vendors | Is that the right boundary? |
Using it in an incident
When a vendor reports a breach, filter the map for that vendor. You get the list of services, the data classes involved, and the owners to call. That lets privacy and legal colleagues start their own assessment with facts. This post does not give legal advice, so involve counsel on any notification question.
Keep it honest
A map drawn once becomes fiction. Rebuild it from the inventory each quarter and compare with outbound traffic. A new destination that does not appear on the map is the signal to investigate.
Try it yourself
In the demo, a dependency inventory shows which components sit in a build. Pick a vendor SDK and draw, on paper, the arrow from your service to its backend and label the data it likely carries.
Click through it at your own pace, or open it full screen.
Quick check
What tool should I draw it in?
Any diagram tool works. Generating it from the inventory file is better, because it stays current.
Do inbound webhooks go on the map?
Yes, with a different line style. They show where outside systems send data into yours.
Safeguard offers SBOM and dependency scanning and asset discovery that can feed this kind of inventory. You can run a free scan at gold.safeguard.sh/scan.
Sources
Last reviewed: 19 October 2026.
