Welcome to our guide on ISO 27001 Annex A 8.23. If you are new to information security, the term web filtering might sound like just another technical hurdle. However, it is actually one of the most practical controls you can put in place to protect your business. At ISO27001.com, we see this control as a vital line of defence against the chaotic nature of the internet.
This control focuses on managing access to external websites. The goal is to reduce the risk of your systems being compromised by malicious content. It also helps prevent users from accessing illegal material. When you implement this well, you create a safer environment for your staff and your data.
Table of contents
Understanding the Basics of Web Filtering
Web filtering is exactly what it sounds like. It acts as a digital gatekeeper. You set specific rules about which websites your employees can visit while they are using company equipment or networks. When a user tries to visit a site, the filter checks the address against your rules. If the site is safe and allowed, the page loads. If it is known to host malware or falls into a blocked category, access is denied.
You do not need to check every single website manually. Modern tools categorize the web for you. They group sites into categories like gambling, social media, adult content, and known malware sources. You simply decide which categories are acceptable for your business needs.
Why This Control Matters to Your Business
The internet is full of threats. A simple click on the wrong link can download ransomware onto a laptop. This can spread to your entire network in minutes. By blocking access to known malicious sites, you stop many attacks before they even start. This is often more effective than relying on antivirus software alone.
There is also a legal aspect to consider. You have a duty of care to ensure your workplace is not used to view illegal content. Web filtering helps you meet these legal obligations. It also prevents productivity loss by limiting access to distracting sites, although security should always be your primary motivation here.
Steps to Implement Web Filtering
Start by writing a clear policy. You need to define what acceptable internet usage looks like for your organization. Be specific about what is allowed and what is not. This document will serve as the foundation for your technical settings. Without a written rule, it is difficult to enforce the technology.
Next, you must choose the right tool. You do not always need expensive enterprise hardware. Many firewalls include filtering features. Cloud services and endpoint protection software also offer robust filtering options. Select a solution that fits your budget and technical capabilities. The tool must be able to update its list of malicious sites automatically.
Once you have the tool, configure your rules. Block categories that pose a high security risk immediately. These usually include hacking sites, known malware hosts, and phishing domains. Then, look at categories that pose legal or productivity risks. Be careful not to block sites that your team needs for their daily work.
Managing Exceptions and Changes
You will face situations where a legitimate website is blocked. This is inevitable. A member of your marketing team might need access to social media. A researcher might need to visit a site that is wrongly categorized. You need a formal process to handle these requests.
Do not just unlock the site verbally. Create a simple log or ticket for the request. Review the site to ensure it is actually safe. If you approve the access, document the reason and the duration. This shows that you are managing the risk rather than just turning off the security.
What the Auditor Expects
As a certification body, we look for evidence that the control is working. When an auditor from ISO27001.com visits, they will not just ask if you have a filter. They will want to see it in action. We expect to see that you have clearly defined rules in your policy. If your policy says you block gambling sites, we will expect your technical configuration to match that statement.
We also look for awareness. Your staff should know that web filtering is in place. They should understand why it is there. It is not about spying on them. It is about keeping the company safe. If an employee sees a block page, they should know who to contact if they believe it is a mistake.
Finally, we check your logs. We want to see that you review the system periodically. Are you checking to see who is trying to access blocked sites? Are you updating your rules as threats change? Evidence of review is just as important as the tool itself.
Common Mistakes to Avoid
The most common mistake is being too restrictive. If you block everything, your staff will find ways to bypass the system. They might use their personal phones or unsafe proxies. This creates “shadow IT” which is much harder to secure. Aim for a balance between security and usability.
Another error is setting it and forgetting it. The internet changes every day. New categories of threats emerge constantly. If you do not review your settings at least once a year, your protection will become outdated. Make web filtering a regular topic in your security management meetings.
Conclusion
Implementing Annex A 8.23 does not have to be complex. It requires a clear policy, a reliable tool, and a process for handling exceptions. By taking these steps, you significantly lower your risk of cyber attacks. You also demonstrate to us at ISO27001.com that you take your internet security seriously. Start with the basics, keep your rules updated, and ensure your staff understands the benefits.