Advanced Filtering

PIX Firewall has built-in traffic filtering features that can block certain types of traffic based on its content. ActiveX and Java applets are two kinds of traffic that can be stopped from reaching the private network via the PIX. Also, using software from Websense, PIX allows for more sophisticated filtering of content based on the types of websites being visited.

Websense runs separately from the PIX Firewall. It contains an extensive database of URLs arranged in various categories. PIX uses the Websense protocol to interact with the Websense server to find out if the URLs contained in the HTTP GET requests passing through it are allowed or not. The Websense server makes this decision based on the policy set on it by the administrator based on the site security policy. Using the Websense server provides the following three elements to the PIX Firewall setup:

• URL filtering allows the PIX Firewall to check outgoing URL requests against the policy defined on the Websense server.

• Username logging tracks the username, group, and domain name on the Websense server.

• Username lookup lets the PIX Firewall use the user authentication table to map the host's IP address to the username.

Using the Websense server to filter malicious URL requests can be resource-intensive on a heavily loaded PIX. Although most of the heavy processing is carried out on the Websense server, the communication still needs to take place from within the PIX Firewall software. PIX gets around some of this slowness by building within itself a cache of URLs and the responses generated for them by the Websense server. This lets faster checks be carried out on the most frequently accessed URLs without needing to consult the Websense server. The size of this cache can be configured on the PIX Firewall. However, using the cache feature does bypass one useful feature of the Websense server: URL logging. URL logging allows the Websense server to log various types of information about the URL and the user associated with it. With caching enabled, this feature is no longer in use.

PIX deals with the Java applets being downloaded within an HTML page by going into the page's HTML code and commenting out the Java applet source code. This way, the end user still receives the web page but does not get the Java applet that is embedded in it.

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