Creating an Address Group allows you to block multiple domains. Included is information on configuring DNS on the NetScreen so that address book items can resolve the DNS to an IP address.
This article applies to ScreenOS 4.0 and higher.
When you block access to websites, you will need to create an Address Group, which includes an address book entry for the DNS name. You can add multiple domain names. For this example, we will block access to www.blockeddomain.com. You will need to configure DNS on the NetScreen before the address book items can resolve the DNS to an IP address.
To block access to websites, perform the following steps:

Open the
WebUI. For more information on accessing the WebUI, go to
Accessing Your NetScreen Using the WebUI.

From the NetScreen options menu, click
Network, and then click
DNS.

In the Host Name, Domain Name, Primary DNS Server, and Secondary DNS Server text boxes, enter your information.
For this example, we have entered a Host Name of ns50, a Domain Name of netscreen.com, a Primary DNS Server of 1.1.1.1, and a Secondary DNS Server of 1.1.1.2.

Click Apply.
From the NetScreen options menu, click Objects, select Addresses, and then click List.


From the interface drop-down menu, select
Untrust, and then click to select
New.


In the
Address Name text box, enter an address name.


Under
IP Address/Domain Name, click to select
Domain Name. In the
Domain Name text box, enter the domain name that you want to block.

In the
Zone drop-down menu, click to select
Untrust.


Click
OK.

From the NetScreen options menu, click
Objects, select
Addresses, and then click
Groups.


From the interface drop-down menu, click to select
Untrust, and then click
New.


In the
Group Name text box, enter a group name.


From
Available Members, click to choose the available member that you would like to add to this group, and then click
<<.

The
Group Members box will now show
www.blockeddomain.com.


Click
OK.

From the NetScreen options menu, click
Policies.


In the
From drop-down menu, click to select
Trust. From the
To drop-down menu, click to select
Untrust.


Click
New.

From
Source Address, click to select
Address Book. From the
Address Book drop-down menu, click to select
Any.


From
Destination Address, click to select
Address Book. From the
Address Book drop-down menu, click to select
www.blockeddomain.com.

From the
Service drop-down menu, click to select
ANY.


From the
Action drop-down menu, click to select
Deny.

Click
OK.

Additionally, the Juniper firewall provides the feature of URL filtering to block the website. For more information, refer to Concepts & Examples ScreenOS Reference Guide, Attack Detection and Defense Mechanisms - Release 6.3.0, Rev. 01 (Web Filtering - Chapter 4).
Also, refer to KB6868 - What is BACKDOOR_DETECTED subcategory?