How do block pages work?

Forcepoint Web Security and Forcepoint URL Filtering | v8.5.x | 29-Apr-2022

A block page is displayed in a user's browser when your software prevents access to a URL or cloud application. The block page has 3 sections:

The header explains that the site or cloud application has been blocked.

The top frame contains the actual block message, including the requested URL or cloud application, and the reason it was blocked.

The bottom frame provides any options that are available to the user, based on the way the site or cloud application has been blocked. The user may be presented with an option to Go Back to the previous page, Continue to the site or cloud application, or Use Quota Time to view the site.

A slightly different block page is presented if the URL is blocked because its category is in the Security Risk class. In this case, the header information indicates that a security risk has been blocked, with an explanation that the URL may pose a security threat.

When a user clicks the More Information button, additional information is displayed on the block page to explain why the request was blocked.

In addition to the visible details displayed on the More Information page, hidden information is added to the block page source code. Administrators can use this data to help with troubleshooting if a user's requests are being blocked unexpectedly.

To access the hidden information on the More Information page:

Right-click inside the top frame and select View Source (Internet Explorer) or This Frame > View Frame Source (Mozilla Firefox).

Scroll down to the bottom of the resulting HTML output. The information includes:

User name and IP address

The policy that was applied

The delegated administrator role associated with the policy

How the categorization was done

For example:

User name: LDAP://10.203.128.200 OU=UA,DC=ua-ux,DC=forcepoint,DC=com/Chinua Achebe Source IP address: 10.203.128.45 Current time: 10:42

This user receives policy: role-8**Security Only. The policy includes a category or limited access filter for the current time.

This client is associated with role: Super Administrator.

The request was categorized by: Master Database.

If a customized block page does not contain the More Information option, the URL that generates the page can be edited. A block page URL looks something like this:

http://<ipaddress>:15871/cgi-bin/blockpage.cgi?ws-session=...

Replace blockpage with moreBlockInfo:

http://<ipaddress>:15871/cgi-bin/moreBlockInfo.cgi?ws-session=...

The page that displays contains the information described in the procedure above.

Note that this information is viewable only if your browser supports iframes.

For information about customizing block pages, see Creating Custom Block Pages.

Why is the block page sometimes blank?

In some cases, a very small, blank image file (BlockImage.gif) is displayed instead of a standard or security block page. This happens when the Advertisements category is blocked, and a site tries to display an image (like a GIF or JPG file) hosted at a URL in the Advertisements category.

In some cases, an entire site may be made up of advertisement images. In this case, the user will see a blank web page in the browser instead of a standard block message. Users can tell that the site has been blocked because of the URL, which is something like this:

http://<Filtering Service IP address>:15871/cgi-bin/blockpage.cgi?ws-session=<session number>

Why is only part of the block page visible?

Most web pages contain content from multiple sources (ad servers, streaming video sites, social networking applications, image hosting services, and so on). Some sites aggregate content, pulling pieces from multiple sites into a single presentation.

In these instances, users may request sites that contain a mix of permitted and blocked content.

When a frame or iframe within a larger page contains blocked content, a standard or security block page is displayed within that frame. When the frame is small, however, the end user might be able to see only a tiny portion of the page (perhaps not even the full block icon), and not understand why the content is blocked.

To address this issue, users can mouse over whatever portion of the block page is visible to see a tooltip-style popup with a brief block message. Clicking the message causes the full block page to appear in a separate window.