Set up a custom blocked URLs list using Office 365 ATP Safe Links

With Office 365 Advanced Threat Protection (ATP), your organization can have a custom list of website addresses (URLs) that are blocked. When a URL is blocked, people who click on links to the blocked URL are taken to a warning page that resembles the following image:

This site is blocked

The blocked URLs list is defined by your organization's Office 365 security team, and that list applies to everyone in the organization who is covered by Office 365 ATP Safe Links policies.

Read this article to learn how to set up your organization's custom blocked URLs list for ATP Safe Links in Office 365.

View or edit a custom list of blocked URLs

ATP Safe Links in Office 365 uses several lists, including your organization's custom blocked URLs list. If you have the necessary permissions, you can set up your organization's custom list. You do this by editing your organization's default Safe Links policy.

  1. Go to https://security.microsoft.com and sign in with your work or school account.

  2. In the left navigation, under Threat management, choose Policy > Safe Links.

  3. In the Policies that apply to the entire organization section, select Default, and then choose Edit (the Edit button resembles a pencil).
    Click Edit to edit your default policy for Safe Links protection
    This enables you to view your list of blocked URLs. At first, you might not have any URLs listed here.
    Blocked URLs list in the default Safe Links policy

  4. Select the Enter a valid URL box, type a URL, and then choose the plus sign (+).

  5. When you are finished adding URLs, in the lower right corner of the screen, choose Save.

A few things to keep in mind

While you add URLs to your list, keep the following points in mind:

  • Do not include a forward slash ( /) at the end of the URL. For example, instead of entering http://www.contoso.com/, enter http://www.contoso.com.

  • You can specify a domain-only URL (like contoso.com or tailspintoys.com). This will block clicks on any URL that contains the domain.

  • You can specify a subdomain (like toys.contoso.com*) without blocking a full domain (like contoso.com). This will block clicks any URL that contains the subdomain, but it won't block clicks to a URL that contains the full domain.

  • You can include up to three wildcard asterisks (*) per URL. The following table lists some examples of what you can enter and what effect those entries have.

Example Entry What It Does
contoso.com or *contoso.com*
Blocks the domain, subdomains, and paths, such as https://www.contoso.com, http://sub.contoso.com, and http://contoso.com/abc
http://contoso.com/a
Blocks a site http://contoso.com/a but not additional subpaths like http://contoso.com/a/b
http://contoso.com/a*
Blocks a site http://contoso.com/a and additional subpaths like http://contoso.com/a/b
http://toys.contoso.com*
Blocks a subdomain ("toys" in this case) but allow clicks to other domain URLs (like http://contoso.com or http://home.contoso.com).

How to define exceptions for certain users in an organization

If you want certain groups to be able to view URLs that might be blocked for others, you can specify an ATP Safe Links policy that applies to specific recipients. See Set up a custom "do not rewrite" URLs list using ATP Safe Links.