Implementing ISO 27001 Annex A 8.12 establishes robust Data Leakage Prevention (DLP) controls to detect and block the unauthorized extraction of sensitive information. By applying active filtering to emails, endpoints, and networks, organizations ensure data confidentiality and minimize the risk of intellectual property theft or regulatory breaches.
ISO 27001 Annex A Data Leakage Prevention Implementation Checklist
Use this implementation checklist to achieve compliance with ISO 27001 Annex A 8.12. Effective Data Leakage Prevention (DLP) is not a policy document; it is a set of active technical controls that physically stop data from leaving your controlled environment.
1. Define Sensitive Data Strings (RegEx)
Control Requirement: Identification and classification of information to be protected from leakage.
Required Implementation Step: Configure your DLP engine with specific Regular Expressions (RegEx) relevant to your data. Do not rely on generic “PII” templates. Input exact patterns for your customer IDs, project codenames, and specific credit card formats to ensure the tool knows exactly what to look for.
Minimum Requirement: You must technically define what “Sensitive Data” looks like in the scanning engine.
2. Enforce USB and Removable Media Blocking
Control Requirement: Prevent unauthorised data copying to physical media.
Required Implementation Step: Use Group Policy (GPO) or your Endpoint Detection and Response (EDR) agent to block write access to all USB mass storage devices by default. Create a whitelist for specific, encrypted, company-issued drives only if absolutely necessary.
Minimum Requirement: “Read-Only” access for USBs; “Write” access must be technically disabled.
3. Configure Email Outbound Filtering
Control Requirement: Monitor and block sensitive data transmission via email.
Required Implementation Step: Configure rules in your email gateway (e.g., Exchange Online, Mimecast) to block messages containing defined sensitive patterns (see Step 1) or more than 5 attachments. Implement a “Policy Tip” that warns users before they click send if sensitive data is detected.
Minimum Requirement: Automated encryption or blocking of emails containing PII or financial data.
4. Restrict Uploads to Personal Cloud Storage
Control Requirement: Prevent exfiltration to unauthorised cloud services.
Required Implementation Step: Configure your web gateway or firewall to block uploads to personal storage categories (e.g., Personal Gmail, Dropbox, WeTransfer). Allow download access if needed for business, but “Post/Upload” actions must be strictly denied to non-corporate tenants.
Minimum Requirement: Network-level blocking of “Shadow IT” storage repositories.
5. Implement Endpoint DLP Agents
Control Requirement: Monitor data movement at the user workstation level.
Required Implementation Step: Deploy host-based DLP agents to all workstations. Configure them to monitor the clipboard, screen capture tools, and file system. Prevent users from copying data from “Corporate” applications (e.g., Salesforce) and pasting it into “Personal” applications (e.g., Twitter/X).
Minimum Requirement: Preventing the “Copy/Paste” of sensitive data between managed and unmanaged apps.
6. Secure Print output
Control Requirement: Prevent leakage of data via hard copy.
Required Implementation Step: Implement “Follow-Me” printing where users must physically authenticate at the printer to release a job. Configure the print server to watermark documents with the username and timestamp of the person printing.
Minimum Requirement: Logs of exactly who printed what document and when.
7. Disable Unsecured Network Protocols
Control Requirement: Prevent data transfer via unencrypted or unmonitored channels.
Required Implementation Step: Block outbound traffic on ports associated with FTP (21), Telnet (23), and legacy SMB. Force all file transfers to occur via SFTP or HTTPS channels that can be inspected by your SSL/TLS decryption appliance.
Minimum Requirement: If you cannot inspect the traffic, you cannot prevent the leak.
8. Tune False Positives and Business Rules
Control Requirement: Minimise disruption to legitimate business activities.
Required Implementation Step: Dedicate a weekly review session to analyse DLP logs. Whitelist legitimate business workflows that are triggering false positives. A DLP system that blocks everything will simply be bypassed or ignored by frustrated users.
Minimum Requirement: Evidence of active tuning; a “Set and Forget” DLP system is useless.
9. Enable Digital Rights Management (DRM)
Control Requirement: Protection of information even after it leaves the network.
Required Implementation Step: Apply Azure Information Protection (AIP) or similar DRM labels that travel with the file. Configure the “Confidential” label to restrict access to authenticated employees only, rendering the file unreadable if leaked to an external party.
Minimum Requirement: Files must require authentication to open, regardless of where they are stored.
10. Establish a Violation Response Process
Control Requirement: Appropriate action must be taken when leakage is detected.
Required Implementation Step: Define the HR and Legal workflow for a confirmed data leak. Automate the alert to the Security Operations Centre (SOC). If a user attempts to copy the customer database to a USB, their account should be automatically disabled pending investigation.
Minimum Requirement: Automated response actions for high-severity data exfiltration attempts.
ISO 27001 Annex A 8.12 SaaS / GRC Platform Implementation Failure Checklist
| Control Requirement | The ‘Checkbox Compliance’ Trap | The Reality Check |
|---|---|---|
| Sensitive Data Definition | GRC tool asks: “Is DLP enabled?” (Yes/No). | You clicked “Yes”, but the default ruleset only looks for US Social Security Numbers. You are a UK company, so it catches nothing. |
| USB Blocking | “We have a policy forbidding USBs.” | A disgruntled sales rep plugs in a 1TB drive and copies the entire CRM database in 5 minutes. Policy didn’t stop them; a GPO would have. |
| Cloud Storage | “We tell staff to use OneDrive.” | Staff use their personal Google Drive to “work from home” more easily. Without technical blocking, your IP is now on their personal server. |
| SSL Inspection | “We have a firewall.” | 80% of web traffic is encrypted (HTTPS). If you aren’t doing SSL inspection, your firewall cannot see the sensitive data inside the packet. |
| Print Security | “We have secure shredding bins.” | The confidential report sat on the printer tray for 4 hours before anyone picked it up. During that time, 50 visitors walked past it. |
| False Positives | Turning on “Block All” mode day one. | The CEO tries to email a contract and gets blocked. They order IT to turn off DLP entirely. Compliance returns to zero. |
| Clipboard Control | Ignoring copy/paste risks. | A user copies a password from LastPass and pastes it into ChatGPT. That credential is now leaked to a third-party model. |
DO IT YOURSELF ISO 27001
STOP SPANKING £10,000s on CONSULTANTS and ISMS ONLINE PLATFORMS
About the author
