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Barracuda Web Filter Release 3.3

38 Chapter 3: Configuring, Monitoring, and Managing the Barracuda Web Filter

You can use the Applications filter as a pre-emptive measure to protect your network against

malware.

For example, you may want to block the IRC application because this type of application often

introduces BOTS into networks. BOTS are automated programs that repeatedly run specific tasks,

and malicious BOTS activity is common in IRC communications.

You can also use the application blocking feature when you hear about a virus spreading over a

specific IM service or tool. In this case, you can proactively protect your network from the infection

by blocking that particular service until the threat has been resolved.

Domain filtering

Use the BLOCK/ACCEPT > Domains page to block (blacklist), warn, monitor, or allow (whitelist)

traffic to specific domains and subdomains.

URL pattern filtering

Use the BLOCK/ACCEPT > URL Patterns page to enter regular expressions or keyword that, if

matched to a URL, will block (blacklist), warn, monitor, or allow (whitelist) that URL. For more

information about using regular expressions, refer to Appendix B, Regular Expressions on page 73.

Examples:

• If you want to block all Web sites that contain porn in the URL, then enter porn as a blocked

pattern.

• Sometimes spyware applications use different hostnames but the same domain name so the

URLs appear to be from different hosts. In this case you can enter the domain name as a pattern

to block all URLs on that domain.

• Another example is if you want to allow access to example.com but want to block

maps.example.com. In this case, specify example.com as an allowed pattern and specify

maps.example.com as a blocked URL (see Domain filtering on page 38).

Tip: Run a test on your regular expressions with special characters before you encode them in a

pattern filter.

Custom categories filtering

Use the BLOCK/ACCEPT > Custom Categories page to create a custom filter, which can consist of

the domain names or built-in Web content categories you select.

Note:

You can select a maximum of three built-in categories per custom category.

Custom categories are used in the same way as the built-in filters:

• You can apply a custom category to either authenticated or unauthenticated users.

• You can define a user- or group- specific exception rule to a custom category policy.

After you define a custom category, allow between five and ten minutes for the Barracuda Web Filter

to compile and then fully activate the new category. To verify that a newly created custom category

is active, you can use the Content Filter Lookup

facility in the Content Filter page, as described in

the online help for the

Custom Categories page.

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Barracuda Networks 4 Especificaciones Pagina 38