Stopping Sensitive Data Going Into AI Tools: DLP for Small Firms

The problem: copy, paste, leak

Most AI data leaks at small firms aren't hacks. They are a staff member pasting a customer list, a payslip or a medical note into a free AI chatbot to 'tidy it up'. Once pasted, that data sits with a provider you have no contract with. The PDPC's Advisory Guidelines on Use of Personal Data in Generative AI set out what organisations using AI should do with personal data, and our guide to a ChatGPT at work policy under the PDPA covers the policy side.

DLP is the technical layer: it recognises sensitive content (NRIC numbers, card numbers, files labelled Confidential) and audits, warns or blocks when someone tries to move it somewhere risky.

What your Microsoft 365 licence includes

Microsoft's Purview service description lists which plans include each DLP feature. The short version for small firms:

Our guide to whether Business Premium is worth it covers what else it adds, such as Intune and Defender.

Endpoint DLP: block pastes into AI websites

If you have the licence, Microsoft's paste-to-browser scenario describes how to evaluate content at the moment it is pasted and audit, warn or block depending on the destination site.

1. 1

   Onboard devices to Purview

   Endpoint DLP only applies to Windows and Mac devices onboarded to Microsoft Purview, usually through Intune.

2. 2

   Create a sensitive service domain group

   In Endpoint DLP settings, add the AI sites you want to control (for example chatgpt.com and gemini.google.com) as a group.

3. 3

   Create the DLP policy

   Choose the sensitive information types (Singapore NRIC, credit card numbers) or sensitivity labels to detect, and under Service domain and browser activities select 'Paste to supported browsers'.

4. 4

   Start in audit, then warn, then block

   Watch what is being pasted for a week or two before blocking, so you don't stop legitimate work.

5. 5

   Cover the browsers staff use

   Microsoft lists Edge, Chrome and Firefox (Chrome and Firefox need the Microsoft Purview extension on Windows) and Safari as supported. Block or manage other browsers.

Microsoft notes the paste control works on the content being pasted regardless of where it came from, which is what you want for chatbot prompts.

Edge for Business and Copilot controls

Microsoft's Edge for Business DLP page says DLP is built into Edge for Business, so devices don't need to be onboarded to Purview. It can stop sensitive data being shared to unmanaged cloud apps such as consumer AI chatbots, billed as a pay-as-you-go Purview feature. If you go this route, make Edge the only allowed browser for work, or the control is easy to bypass.

For Microsoft's own AI, Purview DLP can also be applied to Copilot. Microsoft's DLP for Copilot page describes policies that stop Copilot and Copilot Chat sending sensitive information to external web search, so responses use internal data only. Edge's page context policy, covered in our guide to Gemini in Chrome and Copilot in Edge, decides whether Copilot can read the page a user is on.

Controls that work on any plan

Most small firms get most of the benefit without E5.

• Approve one AI tool with a business agreement, such as Copilot Chat with a work account or a business plan of ChatGPT, Claude or Gemini, and tell staff to use only that.
• Block or warn on other AI sites with your firewall, DNS filter or browser policy. Our guide to finding shadow AI tools shows how to see which ones staff already use.
• Use sensitivity labels (in Business Premium) on Confidential files so they can't be shared outside the company by email or link.
• Manage browsers and extensions so staff can't install AI extensions that read every page.
• Train staff with examples, not rules alone: show what a safe prompt looks like with names and numbers removed.

A never-paste list mapped to the PDPA

Give staff a short list they can remember. It applies to every AI tool, including approved ones, unless your policy says otherwise for a specific, contracted tool.

These map to the kinds of data the PDPA treats with extra care: the PDPC's guidance restricts collecting NRIC numbers, and its breach notification rules treat financial, health and identity data as causing significant harm if leaked. This is general information, not legal advice.

Do it yourself or get help?

Choosing an approved tool, blocking others and publishing the never-paste list can be done in a week without new licences. Endpoint DLP and Edge inline protection are worth it mainly for firms handling large volumes of health, financial or children's data, and they need careful tuning in audit mode first.

Our Microsoft 365 / Google Security Lockdown (S$590) enforces MFA, blocks risky apps and legacy sign-in, sets external sharing rules for files and tidies admin roles; if a feature such as Endpoint DLP needs a licence upgrade, we tell you first. Our Device Encryption & Management (S$490) puts up to 10 devices under Intune or Google endpoint management, which is the prerequisite for any device or browser control.