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Blocking Ultrasurf and HTTPS proxies

It only takes one proxy to put a gaping hole in your network security. Using a web filtering solution that doesn't block proxies is the equivalent of putting a big bolt on your front door but leaving the back door wide open.

There are now millions of proxy anonymizers in existence with miscreants developing new types faster than security vendors can detect and block them. Fortunately, thanks to our development team's commitment to ensure that detection signatures are constantly kept up to date, Guardian has an excellent proxy-blocking record. V2008 Guardian Filters utilize multiple proxy-blocking defenses including SSL [interception and] certificate checking to accurately detect and block secure proxies.

In the last 18 months, the number of types of proxy we detect has quadrupled and this figure will continue to grow as new proxy technologies and variants of existing proxies evolve.

Proxy tools and applications that use HTTPS can be particularly difficult to detect and block because they allow web sites and media files to be viewed secretly within a secure tunnel where content is encrypted.

They also present a much more serious security problem since the secure tunnels they use allow malware and other web-related threats to sneak into networks undetected.

Examples of such 'secure' proxies include Ultrasurf, TOR and VTunnel. These proxy types cannot be blocked using domain or URL blacklists and so the fix that most security vendors recommend is a (far from practical) blanket block on all HTTPS traffic. V2008 Guardian Filters utilize multiple proxy-blocking defenses including SSL/HTTPS Filtering to accurately detect and block secure proxies.

For users of earlier software versions, we recommend creating a whitelist of authorized HTTPS sites and blocking access to the category 'proxies' in Guardian. Disabling direct web access and transparent proxying should also help to avoid proxy abuse.

For more information, please visit the SmoothWall KnowledgeBase.


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