Bluecoat: Different ways to make rules for file extensions

Last Update: 25.06.2008

If you use Bluecoat proxy services (such as Bluecoat SG) in combination with ProxyAV you may sometimes experience problems with certain file extensions. Or maybe you just do not want to let certain extensions get anti virus scanned.

To determine the file extension there are several possibilities. I will show you three ways how to create an object for a file extension.

1. Response Header object
A Response Header Object is the MIME Type answer from the server to the browser. This method is good if you want to set an object for different file extensions with the same purpose. In this example we define the object for the MIME type video/x-flv which includes the file extensions .flv, .f4v, .f4p, .f4a, .f4b.

Image 1: "Rightclick -> Set -> New..."

In Image 1 you see how you create a new Response Header Object.

In the following picture 2 we define the Header/file extension.

Image 2: "Edit Response Header Object"

In this example we define the .flv file extension (Flash Video as you see it for example on YouTube). With this object you are now able to set rules in your Bluecoat Visual Policy Manager.

To do a research of the correct MIME type for your file extension, please visit the MIME Media Types website on IANA.org.

2. Request URL object
Another possibility is to read the file extension out of the URL (web-address) of a file. For example if we request the file http://www.mac.com/safari/safari31.dmg we use the end of the URL to determine the filetype. As you see above in Image 1, set a new object, but this time select "Request URL...".

Image 3: "Edit Request URL Object"

On top, in the field "Name", you simply give a name to this object. It is here named "DMGFile". In the Advanced Match part use "http" as Scheme and as Path just type in your file extension with a leading dot (here: ".dmg"). Do not forget to select "At End" in this row!

3. File extension
The last option is probably the simpliest. Bluecoat offers a list of file extensions. Sounds good! But in most cases the file extension you needed to create a rule for is never found in the (unfortunately really) short file extension list. As you see above in Image 1, you can select the option "File Extensions...".

Image 4: "Add File Extensions Object"

Once again, in the field Name just enter whatever you want to name this object. You can select multiple file extensions if you want. But on this screenshot you also see the problem why you should know options 1 and 2 to create file extension objects. Do you see the .FLV extension somewhere in that list? No? Me neither. But it contains the file extension .FLR - a floor texture file for the game "The Sims". Heaven, we're saved!