You can create a Custom Media Type to reference a Which Media Types clause in the What To Look For? section of a content rule.
The Custom Media Type allows you to define a hexadecimal signature that can be identified at the start or end of a media type file and the offset, in bytes, from the start or end of the file. See Custom Media Type Signatures for further information.
To create a Custom Media Type:
- From the Policy Center Home page, click Custom Media Types. The Manage Custom Media Types page appears.
- Click
New
adjacent to the Filename header. The Modify Custom Media Type page
appears.
- The Overview area enables you to provide a name and optional notes for the Custom Media Type. To edit these details:
- Move the mouse pointer over the Overview area and click Click here to change these settings.
- Edit the Name if required. Clearswift Gateway provides a default name. Change this to something more meaningful, if required.
- Edit the Notes if required. You can insert, change, or delete text in this field, which is empty by default.
- Click Save.
- The Signatures area defines the list of signatures to search on. To add signatures to the list:
- Move the mouse pointer
over the Signatures area and click New.
The Add Signature dialog appears.
- In Signature Pattern, specify a signature to search for. You must enter pairs of hexadecimal characters separated by spaces. See Custom Media Type Signatures for further information.
- Specify whether the Signature Pattern is from the start of the file or end of the file using the drop-down list.
- Specify the Offset value in bytes.
- Click Add to add the signature to the list.
- The signature you defined is listed in the Signatures panel.
- Repeat the above steps for any additional signatures you wish to define.
- To edit or remove a signature
in the list, move the mouse pointer over the Signatures area and select
the signature you wish to edit, then click
Edit
or 
Delete as required. - The Match All Signatures area enables you to match either all or any signatures. To edit these details:
- Move the mouse pointer over the Match All Signatures area and click Click here to change these settings.
- To match either all or any signatures, click the checkbox to Only match if all signatures are detected, as required.
- Click Save.
| When you have finished modifying your content security policy you must apply the configuration for any changes
to take effect. If the |