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/ What Is URL Filtering?

What Is URL Filtering?

URL filtering is a way to prevent access to certain web content through an organization’s network or endpoints. This generally includes blocking malicious websites to protect users and endpoints from cyberattacks. Organizations can also use URL filtering to restrict specific URLs or URL categories that tend to use high bandwidth or hamper productivity, such as social media and streaming video.

What Is URL FIltering?

Why Is URL Filtering Important?

URL filtering is a key element of web security that allows an organization to configure how users access webpages through the network or other systems. It can help to:

  • Protect users and data from security threats such as phishing sites, ransomware, and other malware
  • Rein in bandwidth usage and lost productivity due to use of non-work-related sites or apps
  • Limit the organization’s exposure to liability by blocking access to inappropriate content


Before we continue, let’s clarify some important terms.

What Is a URL?

A Uniform Resource Locator, or URL, is an address that corresponds to the location of a website, database, web application, or protocol (among other things), allowing a web browser to retrieve it.

What’s the Difference Between Web Filtering, URL Filtering, and DNS Filtering?

Web filtering is a broad term for multiple methods of controlling the sites and web apps users can access online. URL filtering and DNS filtering are two of these methods.

Basically, URL filtering blocks URLs (individual webpages) while DNS filtering blocks Domain Name System (DNS) requests and therefore IP addresses (whole websites).


How Does URL Filtering Work?

URL filtering works by applying granular policies that allow or restrict access to particular URLs. Policies can be based on multiple criteria, such as URL categories, specific users or user groups, departments, locations, and time intervals.

When an end user tries to access any URL, the request is compared in real time against active URL filtering policies to determine whether the request is allowed. If access is granted, the page loads normally. If access is denied, the page is prevented from loading, and the user is instead shown a block notification.

Disadvantages of URL Filtering

Although it’s not a functional disadvantage of URL filtering itself, improper policy configuration can lead to over-filtering. For instance, blocking YouTube to keep workers from getting distracted would also stop them from watching video tutorials, slowing them and your organization down while potentially creating more work for your IT helpdesk.

It’s also worth noting that URL filtering alone is not a comprehensive internet security strategy. Modern threat actors can develop new URLs and IP addresses extremely quickly, requiring security strategies that go above and beyond simple block and allow lists of known malicious sites.

How Does URL Filtering Help Block Malware and Phishing?

URL categorization includes much more than just topics like “shopping” or “finance.” Most URL filtering services integrate with a threat intelligence database to enable blocking of URLs flagged as exploitive, malicious, or otherwise dangerous, such as those associated with malware campaigns or phishing attacks.

Various functions work together to give organizations precise control over web access—let’s take a look at these next.

Key Features of URL Filtering

Basic URL filtering solutions allow administrators to customize simple allow and/or block lists to block access to undesired or malicious URLs. Today’s advanced URL filtering tools include these features and more, allowing you to configure:

  • Granular, modular policies: Effective URL filtering policies can be molded to suit the needs and restrictions of multiple groups across an organization. For example, an HR team might need unrestricted access to LinkedIn, but an IT team might not.
  • “Allow” and “block” actions: The basic “green light” and “red light” actions of URL filtering permit or deny access according to policy.
  • “Caution” action: Unlike a block, this action informs a user of potential security risks associated with a request and allows the user to decide whether or not to proceed.
  • “Override” action: Generally reserved for advanced or administrative users, the option to override enables a “block” rule to be bypassed altogether.
  • Duration and bandwidth quotas: Administrators can specify limits on bandwidth consumed and browsing time, after which the action for that URL will change to a more restrictive one (i.e., “caution” or “block”).

Standalone URL Filtering Is Insufficient

While URL filtering is an effective means of blocking malicious websites or restricting specific URLs, it should never be your organization’s only web security solution. Let’s look at the key reasons why:

  • Limited scope of protection: Standalone URL filtering mainly blocks or permits access to websites based on their categorization or reputation. However, it can’t address many modern attacks that exploit other vulnerabilities in web applications, user interactions, or insecure web protocols, such as phishing, drive-by downloads, and malvertising.
  • Lack of advanced threat detection: Many standalone URL filtering solutions lack sandboxing and dynamic analysis capabilities to identify and block sophisticated threats. Cybercriminals continuously develop new techniques to evade traditional security measures, and zero-day threats like these can’t be identified with URL categorization alone.
  • Blind spots in encrypted traffic: URL filtering primarily inspects URL information in plain text, but most web traffic is now encrypted. Cyberattackers often use encryption to bypass traditional security, deliver malware, or exfiltrate data. Cybersecurity solutions such as next-generation firewalls and secure web gateways include HTTPS inspection capabilities.

URL filtering offers some control over web risk, but it can’t providing complete protection against web-based threats. To accomplish that, you need a multilayered approach that includes advanced threat detection, inspection of all encrypted traffic, behavior-based analysis, and more in an integrated platform.

How Zscaler Can Help

Zscaler offers powerful URL filtering as a native feature of Zscaler Internet Access™ (ZIA™), the world’s most deployed security service edge (SSE) platform, along with our industry-leading secure web gatewaydata loss preventioncloud-gen firewall, and more.

Zscaler Internet Access is part of the comprehensive Zscaler Zero Trust Exchange™ platform, which enables fast, secure connections to allow your employees to work from anywhere using the internet as the corporate network.

Key Benefits of URL Filtering from Zscaler

Through native integration with our entire ecosystem, Zscaler URL filtering offers peerless control over your web traffic, including:

  • Dynamic content categorization: Leverage machine learning to determine if uncategorized URLs belong to specific URL categories and apply policy accordingly.
  • Integrated browser isolation: Isolate all traffic to URLs in selected categories through native integration with Zscaler Browser Isolation.
  • Embedded sites categorization: Enforce URL filtering policy for sites translated through services such as Google Translate.
  • Safe search enforcement: Enforce safe results on search engine queries when SSL inspection is enabled by leveraging Zscaler’s unmatched scalability.
  • Granular productivity app controls: Simplify configuration, restrict tenants, and control allowed domains for Microsoft 365 and Google Workspace apps.
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Find out more about URL filtering and the other integrated features of Zscaler Internet Access.

Suggested Resources

Zscaler Help: About URL Filtering
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Zscaler Internet Access
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