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Barracuda Web Security Gateway

Creating Block and Accept Policies

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This article discusses filtering options for blocking and allowing various kinds of web traffic. See also Best Practices in Configuring Policy.

To create exceptions to block/accept policies by specific user, group, or time frame, see Exception Policies. For a video of this article content, scroll to the end of the page.

Content filtering

Barracuda web security products employ a comprehensive database of frequently updated categories of website content types. Use the BLOCK/ACCEPT > Content Filter page to control user access to categories of websites that should be blocked, warned, monitored, or allowed based on content. When you block a category, you block all HTTP and HTTPS traffic to the associated URLs in that category.

For example, http://mail.yahoo.com is categorized as a web-based email site. If you want to block users from accessing their web-based email accounts, block the Web-based Email category.

See Web Use Categories for a listing and definition of content classification.

Safe Search

Safe Search mode prevents a web search engine from displaying objectionable thumbnail images in search results; only filtered thumbnails are displayed in the search results. To limit Safe Search to specific users, create an exception using the BLOCK/ACCEPT > Exceptions page. For details, see How to Enable Safe Search. The entries in this category include search engines which allow users to enable or disable Safe Search mode for image searches. If you enable Safe Search through the Barracuda Web Security Gateway, users cannot use the search engine settings to override this mode. If you only want to enable Safe Search for certain users, select Disable for each search engine listed in the table, or click the All link. On the BLOCK/ACCEPT > Exceptions page, create an Enable exception for the user or group of users for whom you want to enable Safe Search.

Important: Safe Search will not work if the search request is encrypted unless the Barracuda Web Security Gateway is configured to inspect or 'scan' SSL traffic. Google Safe Search requires SSL inspection as searches are encrypted. Using Google Safe Search requires enabling the SSL Inspection feature, which is available for the Barracuda Web Security Gateway 310 and higher. See Using SSL Inspection With the Barracuda Web Security Gateway for details.

Make sure your Barracuda Web Security Gateway is running version 8.1.0.005 or higher before turning on SSL inspection.

Safe Browsing for Schools

Application Filtering

Non Web-Based Applications

Use the BLOCK/ACCEPT > Applications page to block or allow specific application traffic over the HTTP (and HTTPS) protocol that is not browser-based. For example: Skype, Pandora, Adobe Acrobat, FTP. This type of filtering does NOT scan for content. If you need to scan and filter content, you must enable SSL Inspection.

Note that the SSL Inspection feature is only available on the Barracuda Web Security Gateway 310 (limited) and higher, and requires more system resources and installation of SSL certificates to configure. The Barracuda Web Security Gateway 410 and higher is required to block/allow specific functions that run within web applications, such as Facebook games or Skype chat. Configure on the BLOCK/ACCEPT > Web App Control page.

For a user to download or use an application, the user’s application needs to communicate with an external server. When you select to block an application, the Barracuda Web Security Gateway searches for traffic that contains data associated with an application server and then blocks that traffic.

The Barracuda Web Security Gateway 610 Vx virtual machine and higher supports application filtering, social media monitoring, and suspicious keyword alerts.

Social Media and Other Web-Based Applications
Web Application Monitoring

Use this feature to capture and archive chat, email, user registrations and other social media interactions. The archiving repository can be your Barracuda Message Archiver, your Microsoft Exchange Server journaling tool or, for example, a system administrator email address.

For example, you might want to allow users in the organization to use Facebook to view and make status updates and use chat, but you want to capture the content. You might also want to block games, shares and other Facebook apps to protect your network from viruses and malware.

To configure Web Application Monitoring, you'll want to first set up your block/accept policies for web-based applications. Here's the process for this example:

  1. From the BLOCK/ACCEPT > Web App Control page, in the Application Navigator, check Facebook to allow some or all Facebook applications.
  2. Select the Facebook actions to block and allow and save your changes. In this example, you'd leave chat and status update in the Allowed Applications list, moving other applications you want to block, such as shares, games and other apps, to the Blocked Applications list. Save your changes.
  3. From the BLOCK/ACCEPT > Web App. Monitor page, enable the application actions whose content you want to archive. In this example, you would enable Facebook Wall Posts, Chat Message and Private Message. Once you enable any actions on the page, the Barracuda Web Security Gateway will capture the content from each action, package it as an SMTP message and email it to the Notification Email Address you specify.

Domain filtering

Use the BLOCK/ACCEPT > Domains page to blocklist (block), warn, monitor or whitelist (allow) traffic to specific domains and subdomains. Use domain whitelists to allow access to domains that belong to categories that are generally blocked. Note that domains that are whitelisted ARE subject to the MIME type blocking rules you create (see below). Use domain blocklists to restrict access to domains in addition to those specified in other filtering categories.

To control access to a domain and all its associated URLs, make sure you enter the domain identifier. For example, www.example.com will control access only to the specific URL but example.com will control access to all URLs under the domain.

URL pattern filtering

Use the BLOCK/ACCEPT > URL Patterns page to enter regular expressions or keywords that, if matched to a URL, will block (blocklist), warn, monitor, or allow (whitelist) that URL. For more information about using regular expressions, refer to Regular Expressions. Note that URLs that are whitelisted ARE subject to the MIME type blocking rules you create (see below).

Run a test on your regular expressions with special characters before you encode them in a pattern filter.

Examples:

Example 1 – Block all of Facebook except for ONE particular page.
  1. Configure SSL Inspection on the Barracuda Web Security Gateway. See the ADVANCED > SSL Inspection page.
  2. Go to the BLOCK/ACCEPT > Web App Control page and block Facebook as follows:
    1. Check Social Media under Allowed Applications.
    2. In the drop-down below that box, select Facebook all functions.
    3. Click the Block button on the right side of the page.
    4. Click Save.
  3. Go to the BLOCK/ACCEPT > Exceptions page. Create an exception as follows:
    1. Select Allow for the Action.
    2. Select the appropriate group for AppliesTo.
    3. Select URL Patterns for Exception Type.
    4. In the URL Pattern field, paste the Facebook page URL you want to ALLOW. For example:  https://www.facebook.com/thenameofyourpage.html
    5. Configure other Exception rules as desired, such as Time Frame (to Allow), etc.
    6. Click Add.
Example 2 – Block all websites that contain "porn" in the URL
  1. Go to the BLOCK/ACCEPT > Exceptions page. Create an exception as follows:
    1. Select Block for the Action.
    2. Select the appropriate group for AppliesTo.
    3. Select URL Patterns for Exception Type.
    4. In the URL Pattern field, enter  *porn*
    5. Configure other Exception rules as desired, such as Time Frame (to Allow), etc.
    6. Click Add.

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.

Example 3 – Allow access to example.com but block maps.example.com

Follow instructions in the above examples to create an Exception. In this case, specify example.com as an Allowed URL pattern and specify maps.example.com as a Blocked URL pattern.

On the BLOCK/ACCEPT > Exceptions page, when you select the Exception Type as Domain, note that you can only specify one domain per exception. If you want to create exceptions for more than one domain, you must create a separate exception for each one.

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. 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 Security Gateway 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 BLOCK/ACCEPT >Content Filter page, as described in the online help for the BLOCK/ACCEPT > Custom Categories page.

MIME type blocking

Use the BLOCK/ACCEPT > MIME Blocking page to specify standard MIME types that you want to block. Note that websites that are whitelisted ARE subject to the MIME type blocking rules you create. Many organizations choose to block Internet radio and streaming media because they add load to the internal network, as well as executable files because they can install viruses and various other malware. Some examples of MIME Type blocking:

  • To block Internet radio, which uses MPEG (.mpg, mpega, or .abs) or Microsoft audio (.wav) files, enter audio/x-mpeg or audio/x-wav as blocked MIME types.
  • To block streaming media, which uses MPEG video, enter video/mpeg or video/x-msvideo as blocked MIME types.
  • To block access to executables (.exe), enter application/octet-stream as a blocked MIME type.

For more examples of MIME types, click Help on the BLOCK/ACCEPT > MIME Blocking page.

On the BLOCK/ACCEPT > Exceptions page, when you select the Exception Type as MIME Type, note that you can only specify one MIME Type per exception. If you want to create exceptions for more than one MIME type, you must create a separate exception for each type.

 IP-based exemption

If you want to exempt certain clients or sub-networks from all filtering (including spyware filtering), you can use the BLOCK/ACCEPT > IP Block/Exempt page and specify the source IP address for those clients under IP and Port Exemptions. For example, if you want to exempt an executive’s client machine from all filtering, you can do so using the IP address of the client. Similarly, if you want to exempt certain external devices (such as trusted servers outside the protected network), from all filtering, you can specify the destination IP address and specific port under IP and Port Exemptions.

Exempted IP addresses will bypass the following block filters:

  • Content filtering
  • IM blocking
  • All types of download blocking

Exempted IP Addresses will bypass ALL filters including spyware and virus filters.

IP-based blocking

To block ALL IP-based URLs, set Block IP Based URLs to Yes on the BLOCK/ACCEPT > URL Patterns page. The default and recommended value for this setting is No.

If you want to block certain clients or sub-networks from all access, you can use the BLOCK/ACCEPT > IP Block/Exempt page and specify the source IP address for those clients under IP and Port Exemptions. For example, if you want to block traffic from a suspicious client machine or email servers or internal web servers, you can do so using the IP address of the client. Similarly, if you want to block certain external devices, you can specify the destination IP address and specific port under IP and Port Exemptions. Note that when the Barracuda Web Security Gateway is deployed as a forward proxy, IP block/accept rules based on request destination are not applied.

 

This video describes how to block or exempt traffic by IP address in the Barracuda Web Security Gateway.

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