ISO 27001 Annex A 8.12 is a security control designed to prevent the unauthorized extraction or disclosure of sensitive information. It requires organizations to implement data leakage prevention (DLP) measures across systems, networks, and devices to detect and block active leaks—whether accidental or malicious—thereby protecting data at rest, in transit, and in use.
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”:
- Data at Rest: How are you protecting files sitting on hard drives or in cloud repositories? (e.g., Encryption).
- Data in Transit: How are you securing data while it moves? (e.g., Email filtering or TLS).
- 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 |
|---|---|---|
| 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. |
Table of contents
- Key Takeaways: ISO 27001 Annex A 8.12 Data Leakage Prevention
- What is ISO 27001 Annex A 8.12?
- Why is data leakage prevention important?
- ISO 27001 Annex A 8.12 Free Training Video
- ISO 27001 Annex A 8.12 Explainer Video
- ISO 27001 Annex A 8.12 Podcast
- ISO 27001 Annex A 8.12 Implementation Guidance
- How to implement ISO 27001 Annex A 8.12
- Three States of Data that must be protected
- How to comply
- How to pass an ISO 27001 Annex A 8.12 audit
- What will an auditor check?
- Top 3 ISO 27001 Annex A 8.12 mistakes and how to avoid them
- Applicability of ISO 27001 Annex A 8.12 across different business models.
- Fast Track ISO 27001 Annex A 8.12 Compliance with the ISO 27001 Toolkit
- ISO 27001 Annex A 8.12 FAQ
- Related ISO 27001 Controls
- Further Reading
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.
ISO 27001 Annex A 8.12 Implementation Guidance
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.
How to implement ISO 27001 Annex A 8.12
Implementing Data Leakage Prevention (DLP) is a critical technical requirement for identifying, monitoring, and protecting sensitive information from unauthorised disclosure. By following these action-oriented steps, your organisation can establish a robust DLP framework that satisfies ISO 27001 Annex A 8.12 while mitigating the risks of data breaches across endpoints, networks, and cloud environments.
1. Formalise Data Classification and DLP Policies
- Identify and categorise sensitive data sets, such as PII, intellectual property, and financial records, to establish the technical scope for DLP rules.
- Draft a formal Data Leakage Prevention Policy that defines the “Rules of Engagement” (ROE) for data movement and the legal basis for monitoring in compliance with the UK GDPR.
- Result: A documented governance framework that ensures technical DLP controls are aligned with organisational risk appetite and legal obligations.
2. Provision Endpoint and Network DLP Monitoring Tools
- Deploy DLP agents to all organisational endpoints to monitor and block unauthorised data transfers to USB devices, cloud storage, or personal email.
- Implement network-level DLP gateways to inspect outbound traffic, including encrypted HTTPS streams, for sensitive data patterns or unauthorised file uploads.
- Result: Comprehensive visibility into data-in-motion and data-at-rest, preventing accidental or malicious exfiltration at the source.
3. Restrict Access via Granular IAM Roles and MFA
- Enforce the Principle of Least Privilege by assigning specific Identity and Access Management (IAM) roles to users based on their need to handle sensitive data.
- Mandate Multi-Factor Authentication (MFA) for accessing high-risk data repositories to ensure that a compromised credential alone cannot lead to a massive data leak.
- Result: A hardened access layer that reduces the likelihood of internal data misuse and protects against external account takeover attempts.
4. Execute Automated Content Discovery and Hashing
- Schedule automated scans of file shares, databases, and cloud environments to discover “dark data” that lacks appropriate security labels.
- Utilise cryptographic hashing or digital “fingerprinting” to identify exact matches of sensitive documents, ensuring they cannot be renamed or slightly modified to bypass filters.
- Result: Accurate identification of sensitive assets across the entire estate, ensuring that protection follows the data wherever it resides.
5. Revoke Unauthorised Third-Party Data Sharing Permissions
- Perform regular technical audits of SaaS and cloud environment sharing settings to identify and revoke “Public” or “Anyone with the link” access.
- Implement Cloud Access Security Broker (CASB) policies to automatically block the sharing of sensitive files with unverified external domains.
- Result: Elimination of unintentional data exposure caused by misconfigured cloud collaboration tools or shadow IT.
6. Implement Centralised Incident Response and SIEM Logging
- Configure DLP systems to export all “Block” or “Alert” events to a centralised Security Information and Event Management (SIEM) platform for real-time analysis.
- Establish a formal incident response workflow for DLP violations, including automated notifications for the Data Protection Officer (DPO) when PII is involved.
- Result: Enhanced situational awareness and a verifiable audit trail for ISO 27001 compliance and post-incident forensic investigations.
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
- 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.
- 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.
- 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
- 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.
- 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.
- 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.
Applicability of ISO 27001 Annex A 8.12 across different business models.
| Business Type | Applicability | Examples of Control Implementation |
|---|---|---|
| Small Businesses | Focuses on protecting high-risk data (like customer PII or payroll) from accidental leaks. It involves setting up basic guardrails within existing productivity suites to prevent common mistakes. |
|
| Tech Startups | Essential for protecting proprietary source code and rapidly scaling customer databases. Focus is on automated monitoring of cloud channels and SaaS integrations to prevent deliberate theft or “Shadow IT” leaks. |
|
| AI Companies | Critical for protecting high-value model weights and curated training datasets. Focus is on preventing “Prompt Injection” leakage and the unauthorized exfiltration of large-scale data assets. |
|
Fast Track ISO 27001 Annex A 8.12 Compliance with the ISO 27001 Toolkit
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.
| Compliance Factor | SaaS Compliance Platforms | High Table ISO 27001 Toolkit | Audit Evidence Example |
|---|---|---|---|
| Strategy Ownership | Rents access to your policies. If you cancel, you lose the “rules” of your data protection strategy. | Permanent Ownership: Fully editable Word/Excel policies that you own forever on your own systems. | An Information Classification Scheme stored on your internal server, accessible during any audit. |
| Implementation | Requires complex “integrations” that often duplicate work done in Microsoft Purview or Google Workspace. | Governance-First: Formalizes your existing OS and cloud settings into an auditor-ready framework. | A signed risk assessment justifying why USB ports are disabled across the finance department. |
| Cost Structure | Often scales with “endpoints” or “data volume,” creating a recurring tax on your growth. | One-Off Fee: A single payment covers 10 devices or 1,000. No per-seat or per-asset fees. | Saving thousands in OpEx to invest in actual technical DLP tools like endpoint encryption. |
| Vendor Freedom | Limited to specific tool “hooks.” Switching security vendors requires reconfiguring the compliance platform. | Tech-Agnostic: Procedures adapt to any environment (On-prem, Cloud, or Hybrid) without limitations. | The ability to switch from one email filter to another without needing to pay for a new compliance module. |
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.
ISO 27001 Annex A 8.12 FAQ
What is ISO 27001 Annex A 8.12 Data Leakage Prevention?
ISO 27001 Annex A 8.12 is a preventive and detective information security control designed to stop the unauthorized extraction or disclosure of sensitive data. It requires organizations to implement measures across systems, networks, and devices to ensure data is not leaked either accidentally or maliciously.
- Scope: Applies to all devices and networks that process, store, or transmit sensitive information.
- Goal: To detect active leaks and prevent them before data leaves the organization’s control.
- Control Type: It functions as both a #Preventive and #Detective control within the ISO framework.
What are the specific requirements for complying with Control 8.12?
Compliance requires a risk-based approach to identifying, monitoring, and controlling the flow of sensitive information within your organization. You must demonstrate that you have applied technical or procedural measures to stop data from leaving authorized boundaries.
- Identification: You must first identify and classify sensitive data (e.g., PII, financial records).
- Monitoring: Monitor channels where leakage often occurs, such as email, cloud uploads, and removable media.
- Restriction: Apply active blocks or warnings, such as disabling USB ports or filtering email attachments.
Is a dedicated DLP software tool mandatory for ISO 27001 compliance?
No, ISO 27001 does not explicitly mandate purchasing a specific “DLP tool,” but it does require effective measures that often make such tools necessary for larger organizations. Small businesses may achieve compliance through native operating system configurations and strict policy enforcement.
- Native Controls: You can use existing tools like Microsoft Purview, Google Workspace DLP, or Group Policy Objects (GPO) to disable USBs.
- Risk-Based: If your risk assessment shows a high likelihood of leakage, automated tools are the expected standard of care.
- Policy vs. Tool: The standard requires the outcome of prevention, whether achieved through software, hardware configuration, or strict physical controls.
What are the “Three States of Data” that must be protected under Annex A 8.12?
To fully satisfy Control 8.12, auditors expect to see protection measures applied to data in three distinct states: At Rest, In Transit, and In Use. Neglecting any one state creates a vulnerability gap that can lead to non-conformity.
- Data at Rest: Protects files stored on hard drives, USBs, or cloud servers (e.g., Full Disk Encryption).
- Data in Transit: Protects data moving between locations (e.g., Email TLS encryption, blocking unsecure file transfers).
- Data in Use: Protects data currently being accessed or manipulated (e.g., disabling copy/paste buffers, preventing screenshots).
What are common examples of Data Leakage Prevention measures?
Effective measures range from physical restrictions to advanced software filtering rules that block actions based on data sensitivity. These controls should be implemented based on the specific risks associated with your business processes.
- Email Filtering: Automatically blocking emails sent to public domains (e.g., @gmail.com) if they contain “Confidential” attachments.
- Device Control: Physically or logically disabling USB ports to prevent data download to personal thumb drives.
- Web Blocking: preventing uploads to unauthorized cloud storage sites like Dropbox or personal Google Drive.
- Print Restrictions: requiring PIN authentication at printers to ensure sensitive documents are not left unattended.
How should we handle false positives when implementing DLP controls?
You should implement DLP controls in “Monitoring Mode” first to tune your rules before switching to “Blocking Mode.” Immediate strict blocking often disrupts legitimate business workflows and frustrates employees.
- Baseline Phase: Run tools silently to log what data is moving and identify valid business patterns.
- Refinement: Adjust rules to exclude legitimate transfers (e.g., sending data to a known payroll provider).
- Feedback Loop: Allow users to provide a justification if a legitimate action is blocked, allowing IT to update the policy.
Related ISO 27001 Controls
Further Reading
