We have all been there. That split-second of panic when you realise you’ve accidentally hit “Reply All” on a sensitive email, or the sinking feeling when you hear about a USB drive left on a train. In the world of information security, these aren’t just embarrassments; they are data leaks.
With the update to ISO 27001:2022, the standard has introduced a specific control to tackle this head-on: Annex A 8.12 Data Leakage Prevention (DLP). If you are scratching your head looking at this new control, don’t worry. It doesn’t necessarily mean you need to go out and spend a fortune on enterprise-grade software immediately. Let’s break down exactly what this control is and how you can implement it practically.
Table of contents
What is Annex A 8.12?
In the simplest terms, Annex A 8.12 requires organisations to apply measures to prevent the unauthorised disclosure or extraction of information. It falls under the “Technological Controls” category, but as we will discuss, solving it requires a mix of technology, policy, and people.
The goal is to detect and block the unauthorized transfer of data before it leaves your control. This covers everything from a disgruntled employee downloading the customer database to a well-meaning HR manager emailing a spreadsheet of salaries to the wrong “John”.
Step 1: Know Your Data (Discovery and Classification)
You cannot stop data from leaking if you don’t know what it is or where it lives. Before you even look at a DLP tool, you need to look at your data.
This links directly to Annex A 5.12 (Classification of Information). You need to identify what constitutes “sensitive” data for your business. Is it Personal Identifiable Information (PII)? Intellectual Property (IP)? Financial records?
Once identified, you need to know where it resides. Is it on local laptops? SharePoint? A CRM system? If you don’t have a clear asset inventory, you are building a fence in the dark.
Step 2: Assess Your Leakage Channels
Data is like water; it tries to flow everywhere. To implement Annex A 8.12 effectively, you need to identify the “pipes” through which data leaves your organisation. Common leakage channels include:
- Email: The most common culprit. Sending files to personal addresses or wrong recipients.
- Cloud Storage: Uploading work files to personal Google Drive or Dropbox accounts.
- Removable Media: USB sticks and external hard drives.
- Hard Copy: Don’t forget the printer! Sensitive documents left on the tray are a classic leak.
- SaaS Applications: Copy-pasting data into ChatGPT or other online tools.
Step 3: Define Your Rules (Policy and Procedures)
Before buying technology, you need to set the rules of the road. What is allowed and what isn’t? An auditor will expect to see a clear policy that outlines how data leakage is managed.
Your policy should state, for example, that “Strictly Confidential” data cannot be stored on USB drives or emailed externally without encryption. If you need a head start on drafting these documents, Hightable.io offers robust ISO 27001 toolkits that include templates specifically designed for these new Annex A controls. Using a proven template can save you hours of drafting time and ensure you don’t miss the nuances of the 2022 update.
Step 4: Implement Technical Controls
Now we get to the “Prevention” part. Depending on your size and budget, this can range from simple configuration changes to dedicated software.
Endpoint Controls
You can configure your company laptops to disable writing to USB drives for most users. This is a highly effective, low-cost way to stop mass data exfiltration.
Email Filtering
Most modern email platforms (like Microsoft 365 or Google Workspace) have built-in DLP features. You can set up rules that warn a user or block the email if it detects patterns like Credit Card numbers or keywords like “Confidential” going to external domains.
Cloud Security
Restrict which domains your users can share files with. For example, configure your OneDrive or SharePoint so that files can only be shared with whitelisted partner organisations.
Step 5: Monitoring and Incident Response
DLP is not a “set it and forget it” tool. You need to monitor the alerts. If you set your DLP to “Block” immediately, you might stop legitimate business work (false positives), which frustrates staff.
A common implementation strategy is to start in “Monitor Only” mode. Watch the logs for a few weeks to understand how data flows in your business. Once you are confident you won’t grind operations to a halt, switch to “Warn” (letting the user justify the action), and finally to “Block” for high-risk activities.
Also, ensure your Incident Response Plan (Annex A 5.26) is updated to handle DLP alerts. If the system flags that someone is downloading 5GB of data on a Friday night, who gets the alert, and what do they do?
Step 6: The Human Firewall
Technology fails. Policies get ignored. Your last line of defence is your people. Regular awareness training is vital.
Explain why these controls are in place. Employees often circumvent DLP controls not because they are malicious, but because they are trying to do their job and the security controls are getting in the way. If you explain the risks of data leaks (fines, reputation damage, job losses), they are more likely to act responsibly.
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Conclusion
Implementing ISO 27001:2022 Annex A 8.12 is about visibility and control. It starts with understanding your data, defining clear boundaries, and supporting those boundaries with the right mix of technology and culture.
Don’t try to boil the ocean. Start by protecting your most critical data types and the most obvious exit points (like email and USBs). Over time, you can refine your rules and tighten your controls. And remember, if you need help structuring your documentation, resources like Hightable.io can provide the framework you need to get certified with confidence.
About the author
Stuart Barker is a veteran practitioner with over 30 years of experience in systems security and risk management.
Holding an MSc in Software and Systems Security, Stuart combines academic rigor with extensive operational experience. His background includes over a decade leading Data Governance for General Electric (GE) across Europe, as well as founding and exiting a successful cyber security consultancy.
As a qualified ISO 27001 Lead Auditor and Lead Implementer, Stuart possesses distinct insight into the specific evidence standards required by certification bodies. He has successfully guided hundreds of organizations – from high-growth technology startups to enterprise financial institutions – through the audit lifecycle.
His toolkits represents the distillation of that field experience into a standardised framework. They move beyond theoretical compliance, providing a pragmatic, auditor-verified methodology designed to satisfy ISO/IEC 27001:2022 while minimising operational friction.
