ISO 27001:2022 Annex A 8.12 Data leakage prevention

In this guide, I will show you exactly how to implement ISO 27001 Annex A 8.12 and ensure you pass your audit. You will get a complete walkthrough of the control, practical implementation examples, and access to the ISO 27001 templates and toolkit that make compliance easy.

I am Stuart Barker, an ISO 27001 Lead Auditor with over 30 years of experience conducting hundreds of audits. I will cut through the jargon to show you exactly what changed in the 2022 update and provide you with plain-English advice to get you certified.

Key Takeaways: ISO 27001 Annex A 8.12 Data Leakage Prevention

ISO 27001 Annex A 8.12 is a technical control introduced in the 2022 update. It requires organizations to implement measures that detect and prevent the unauthorised disclosure or extraction of sensitive information. The goal is to stop data from “leaking” out, whether through accidental mistakes (like emailing the wrong person) or deliberate theft (like downloading a database to a USB drive).

Core requirements for compliance include:

• Discovery and Classification: You cannot stop data from leaking if you don’t know where it is. You must first identify your “sensitive” data (e.g., PII, IP, or financial records) and classify it accordingly.
• Monitoring Data Channels: You must monitor the “pipes” where data typically leaves the business. This includes email, cloud storage (like Dropbox/Google Drive), removable media (USBs), and even web-based tools like ChatGPT.
• Preventive Controls: You should implement technical measures to block unauthorized transfers. Examples include blocking the use of unencrypted USBs or setting up email rules that prevent “Confidential” files from being sent to external domains.
• Proportionate Response: The standard doesn’t mandate “blocking everything.” Controls should be risk-based; start in “Monitoring Mode” to understand data flow before moving to “Blocking Mode” to avoid disrupting legitimate business work.

Audit Focus: Auditors will look for “The Three States of Data”:

1. Data at Rest: How are you protecting files sitting on hard drives or in cloud repositories? (e.g., Encryption).
2. Data in Transit: How are you securing data while it moves? (e.g., Email filtering or TLS).
3. Data in Use: How are you preventing data from being “leaked” while someone is working on it? (e.g., Clipboard/copy-paste restrictions).

Common Data Leakage Channels:

Channel	Typical Risk	ISO 27001 Prevention Measure
Email	Sending PII to the wrong recipient.	Automated warning prompts or blocking rules.
Cloud Storage	Uploading files to personal accounts.	Restricting file-sharing to approved domains only.
USB/Media	Downloading data to a thumb drive.	Disabling USB ports or enforcing encryption.
SaaS/AI Tools	Pasting code/data into public tools.	Acceptable Use Policies and Web Filtering.

What is ISO 27001 Annex A 8.12?

ISO 27001 Annex A 8.12 is about data leakage which means making sure that devices are protected to stop information being taken or read by people it should not be.

ISO 27001 Annex A 8.12 Data Leakage Prevention is an ISO 27001 control that requires an organisation to stop data from being extracted or leaked from systems. This is usually done as a result of known weakness or having services and functionality enabled that is not needed and is easy to manipulate.

ISO 27001 Annex A 8.12 Purpose

ISO 27001 Annex A 8.12 is preventive control and a detective control that is to detect and prevent the unauthorised disclosure and extraction of information by individuals or systems. 

ISO 27001 Annex A 8.12 Definition

The ISO 27001 standard defines ISO 27001 Annex A 8.12 as:

Data leakage prevention measures should be applied to systems, networks and any other devices that process, store or transmit sensitive information. 

– ISO 27001:2022 Annex A 8.12 Data Leakage Prevention.

Why is data leakage prevention important?

Data leakage is a common way for people to gain access to information that they should not. Rather than rely on hacking or technical exploits it usually relies on the mis use of genuine product features. By applying policy, procedure and control based on an understanding of risk and business requirement can reduce the likelihood of information falling into the wrong hands.

ISO 27001 Annex A 8.12 Free Training Video

In the video ISO 27001 Data Leakage Prevention Explained – ISO27001:2022 Annex A 8.12 I show you how to implement it and how to pass the audit.

ISO 27001 Annex A 8.12 Explainer Video

In this beginner’s guide to ISO 27001 Annex A 8.12 Data Leakage Prevention, ISO 27001 Lead Auditor Stuart Barker and his team talk you through what it is, how to implement in and how to pass the audit. Free ISO 27001 training.

ISO 27001 Annex A 8.12 Podcast

In this episode: Lead Auditor Stuart Barker and team do a deep dive into the ISO 27001:2022 Annex A 8.12 Data Leakage Prevention. The podcast explores what it is, why it is important and the path to compliance.

How to implement ISO 27001 Annex A 8.12

You are going to have to ensure that you:

• Identify the information that you want to protect
• Classify the information that you want to protect
• Implement controls to protect the information based on risk, classification and business need
• keep records
• Test the controls that you have to make sure they are working

There are several approaches to data leakage prevention and the most common is to implement a data leakage prevention tool.

Data Leakage Prevention Tool

A Data Leakage Prevention Tool (DLP) is a specific tool that has been designed to track, detect and protect information based on rules using technology.

These tools can often be applied to structured and unstructured data. They can detect and / or prevent the disclosure of sensitive data for example sending information to, or from, personal and cloud emails, and sending information to cloud storage devices.

The more traditional examples of data leakage prevention are the locking down, or preventing the use of, attached media such as external hard drives and USB devices. Also the restricting of printing.

Implementing a DLP tool will take some planning. It can be easy to implement a tool that prevents people from being able to carry out their role. Spending time to understand what people need to do and then implementing proportionate controls is the key.

A good approach to implementing a DLP tool would be to first implement it in monitoring mode and to analyse the results before turning on more restrictive controls. The ability to request access or appeal a blocked control will help maintain the smooth operation of the business.

It is also important to consult with your legal team and ensure that what ever you do it is within the bounds of all laws and regulations. To do their job correctly, DLP tools will have access to all data and often the personal data of employees and customers.

Some things cannot be covered directly in a DLP tool. Taking screen shots, the use of cameras, video streaming of screens should be addressed in terms and conditions of employment, policies, training, education and physical controls such as not allowing cameras or phones into the work environment.

Backups can be a source of data leakage so having a strong backup policy that requires backups to be encrypted should be considered.

Three States of Data that must be protected

• Data at Rest: (Files on a hard drive/USB). Protection: Encryption/Disk Checks.
• Data in Transit: (Sending an email/uploading to cloud). Protection: Email Filtering/TLS.
• Data in Use: (Opening a file/Copy-pasting). Protection: Clipboard restrictions/Screenshots disabled.

How to comply

To comply with ISO 27001 Annex A 8.12 you are going to implement the ‘how’ to the ‘what’ the control is expecting.
In short measure you are going to:

• Understand and record the legal, regulatory and contractual requirements you have for data
• Conduct a risk assessment
• Based on the legal, regulatory, contractual requirements and the risk assessment you will implement an
  information classification scheme
• Implement and communicate your topic specific policy on access control
• Document and implement your processes and technical implementations for data leakage prevention
• Check that the controls are working by conducting internal audits

How to pass an ISO 27001 Annex A 8.12 audit

To pass an audit of ISO 27001 Annex A 8.12 Data leakage prevention you are going to make sure that you have followed the steps above in how to comply.

You are going to do that by first conducting an internal audit, following the How to Conduct an ISO 27001 Internal Audit Guide.

What will an auditor check?

The audit is going to check a number of areas. Lets go through the main ones

1. That you have documentation

What this means is that you need to show that you have documented your legal, regulatory and contractual requirements
for data leakage prevention. Where data protection laws exist that you have documented what those laws are and what those
requirements are. That you have an information classification scheme and a topic specific policy for access control and
that you have documented your data leakage prevention techniques.

2. That you have have implemented data leakage prevention appropriately

They will look at systems to seek evidence of data leakage prevention. They will review endpoints to see that it is installed. System generated reports and logs will be reviewed. Process documents will be read and processes observed to ensure the documents are being followed. Examples of where the DLP has caught and handled something will be sought.

3. That you have conducted internal audits

The audit will want to see that you have tested the controls and evidenced that they are operating. This is usually in the form of the required internal audits. They will check the records and outputs of those internal audits.

Top 3 ISO 27001 Annex A 8.12 mistakes and how to avoid them

In my experience, the top 3 mistakes people make for ISO 27001 Annex A 8.12 Data leakage prevention are

1. You block everything

This is a common mistake we see. That the teams in charge of the data leakage prevention tool become a bit over zealous and lock everything down causing annoyance, irritation and preventing the business from operating. Be sure to implement proportionately.

2. You don’t know your legal obligations

This is a massive mistake that we see, where people assume ISO 27001 is just information security and forget that it also checks that appropriate laws are being followed, and in particular data protection laws. Cost saving by not having a data protection expert or ignoring data protection law entirely is a common mistake we see people make when cutting corners and saving costs.

3. Your document and version control is wrong

Keeping your document version control up to date, making sure that version numbers match where used, having a review evidenced in the last 12 months, having documents that have no comments in are all good practices.

Fast Track Compliance with the ISO 27001 Toolkit

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For ISO 27001 Annex A 8.12 (Data leakage prevention), the requirement is to detect and prevent the unauthorised extraction of information. While SaaS compliance platforms often try to sell you “DLP integrations” or automated scanning modules, they cannot actually block a USB port or encrypt a hard drive, they are merely a place to host your documentation.

The High Table ISO 27001 Toolkit is the logical, time-saving solution because it provides the governance framework, the policies, classification schemes, and risk assessments, that prove to an auditor you are preventing data leaks, without the cost of an online platform.

1. Ownership: You Own Your Data Protection Strategy Forever

SaaS platforms act as a middleman for your compliance evidence. If you define your data protection rules and store your evidence inside their proprietary system, you are essentially renting your own security strategy.

• The Toolkit Advantage: You receive the Data Protection Policy and Information Classification Scheme in fully editable Word/Excel formats. These files are yours forever. You maintain permanent ownership of your strategy and audit history on your own systems, ensuring you are audit-ready without being held to a subscription “ransom.”

2. Simplicity: Governance for the Tools You Already Use

Annex A 8.12 is about applying measures to your specific systems and networks. You don’t need a complex new software interface to manage what your OS and cloud provider (like Microsoft Purview or Google Workspace DLP) already do.

• The Toolkit Advantage: Your IT team already has the technical ability to restrict USBs or filter emails. What they need is the governance layer to prove to an auditor that these actions are based on risk and classification. The Toolkit provides the pre-written policies and checklists that formalize your technical controls into an auditor-ready framework, without forcing your team to learn a new software platform.

3. Cost: A One-Off Fee vs. The “Data Volume” Tax

Many SaaS compliance tools charge based on the number of “assets” or “endpoints” you monitor. For a control that applies to every device in your organization, these monthly costs can become a significant financial drain.

• The Toolkit Advantage: You pay a single, one-off fee for the entire toolkit. Whether you are protecting 10 devices or 1,000, the cost of your DLP Governance Documentation remains the same. You save your budget for the actual technical DLP tools rather than an expensive compliance dashboard.

4. Freedom: No Vendor Lock-In for Your Security Stack

SaaS tools often have limited “hooks” into specific technical platforms. If you adopt a new security tool or change your cloud provider, you may find the SaaS platform can’t keep up, forcing you to change your security stack to fit your compliance tool.

• The Toolkit Advantage: The High Table Toolkit is 100% technology-agnostic. You can edit the DLP Procedures to match any technical environment. You maintain total freedom to evolve your security infrastructure without being constrained by the technical limitations of a rented SaaS platform.

Summary: For Annex A 8.12, an auditor wants to see that you have a policy for what is protected and proof that your controls are working. The High Table ISO 27001 Toolkit provides the governance framework to satisfy this requirement immediately. It is the most direct, cost-effective way to achieve compliance using permanent documentation that you own and control.

Related ISO 27001 Controls

ISO 27001 Clause 7.3 Awareness

ISO 27001 Annex A 8.15 Logging

ISO 27001 Annex A 8.16 Monitoring Activities

Further Reading

ISO 27001 Information Security Policy Beginner’s Guide

ISO 27001 Data Protection Policy Template

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.