8.23 Web filtering
The organization is to manage which external websites can be reached, so that exposure to malicious content falls. Purpose: keep malware from compromising systems and stop people reaching web resources they are not authorized to use. Guidance: reduce the risk of personnel visiting sites with illegal content or known to host viruses or phishing, for example by blocking the IP addresses or domains concerned, which some browsers and anti-malware tools do automatically or can be set to do. Identify which kinds of website personnel should and should not reach, and consider blocking sites with upload functions unless there is a valid business reason, known or suspected malicious sites distributing malware or phishing, command and control servers, malicious sites identified through threat intelligence (5.7), and sites sharing illegal content. Before deploying filtering, set rules on using online resources safely and properly, including restrictions on undesirable or inappropriate sites and web applications, and keep them current. Train personnel to use online resources safely and properly, covering the rules, the contact point for security concerns and the exception process for reaching restricted resources for legitimate business reasons, and on not overriding browser warnings that a site is insecure. Other information: web filtering can use signatures, heuristics, lists of sites or domains that are allowed or prohibited, and bespoke configuration, to keep malicious software and activity off the network and systems.
Source: ISO/IEC 27002:2022, 8.23. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open ISO/IEC 27002:2022 in the compliance library.
ISO/IEC 27002 is guidance on the Annex A controls; certification is against ISO/IEC 27001. Use this set when your sheet follows the 27002 numbering.
These are the artefacts auditors commonly ask for on this requirement, our guidance rather than text from the standard. Your assessor decides what is sufficient in your context, and asks for samples across the period when a report covers one.
system holds itEvidence a system already holds
- Current rules on safe, proper use of online resources · Endpoint management (MDM / EDR)
- Web filtering or secure web gateway configuration showing blocked categories such as malicious, phishing, command and control, illegal content and upload sites · Endpoint management (MDM / EDR)
periodic reviewEvidence produced at each review
- Training records covering web use rules, reporting contacts, exceptions and not overriding browser security warnings · HR system / LMS
- Coverage evidence that filtering applies to remote and roaming devices as well as on-site traffic · Endpoint management (MDM / EDR)
governing documentDocuments that govern the control
- Integration of threat intelligence feeds into block lists · Policy repository / GRC workspace
- The exception request and approval process with records of approved exceptions · Policy repository / GRC workspace
First move
Common gaps auditors find
- Filtering applies only on the office network, not to remote workers
- Upload and file-sharing sites are open to all users without a business reason
- Users routinely click through browser security warnings
- Block lists are static and not updated from threat intelligence
Do this for your whole sheet
Paste the rows you run your controls from and get this mapping for every control at once, with the periodic-review ones flagged and a first move per row. No account for the first run.
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