Url Filtering - Allied Telesis AR Series Technical Manual

Feature Overview

URL filtering

This feature is supported in AlliedWare Plus version 5.4.6 or later.
URL filtering provides an option for controlling access to website URLs.
Access to particular websites can be allowed (whitelist) or blocked (blacklist), providing businesses
with simple website access management.
URL filtering blocks all HTTP and HTTPS access to a list of websites or portions of web sites.
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A whitelist is a list of URLs that are known to comply with organisational policies.
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A blacklist is a list of URLs that are known to violate organisational policies.
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Kaspersky is a subscription-based service that classifies websites among dozens of pre-defined
categories of content that will not comply with some organisations' policies. 
If you subscribe to the Kaspersky service, you can create additional blacklists to block extra URLs
or whitelists to allow URLs that the Kaspersky service blocks.
The white and black lists can be from two sources, which can be used simultaneously. You can
specify a short list of websites to control access to (up to 1000 blacklist and 1000 whitelist rules),
and/or subscribe to the blacklist service offered by Kaspersky.
If Kaspersky-sourced lists are being used, the device will automatically download list updates from
the Allied Telesis update server.
URL Filtering provides a fast efficient (stream-based) method of blocking web traffic from locations
that are known to be undesirable. It acts on a global basis and should be used when traffic is to be
blocked for everyone on the blacklist, or allowed for selective URLs as configured in a whitelist.
This contrasts with Web Control, which has finer grained control as URLs are proxied and
categorized and access to websites are controllable on a per-category and per-firewall entity basis.
And since the Web Control service is proxy-based there is increased latency compared to the
(stream-based) URL Filtering service.
It is possible to use Web Control and URL Filtering at the same time. Connections must be permitted
by both URL Filtering and Web Control in order to be allowed through the device. A block action in
either feature will cause a failure to load the web page.
How Does URL Filtering Work?
URL filtering works by sniffing traffic as it traverses the AR-Series firewall and detecting the HTTP
and HTTPS transactions that are taking place. These transactions are then processed, and when an
HTTP Request is detected, the URL in question is compared against the whitelists (if any) and
blacklists configured.
In AlliedWare Plus version 5.4.7-1 and later, the URL Filtering feature includes the ability to filter
SSL-protected websites. For these HTTPS requests, the original URLs are encrypted, therefore they
C613-22104-00 REV B
Advanced Network Protection
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URL filtering Page 20