Custom Media Types is a list of one or more hexadecimal signatures that can identify a sequence of bytes in a specific position within a file. The position is defined by the offset from either the start or end of the file. It defines a list of hexadecimal signatures that Secure Web Gateway looks for when the list is referenced from a Which Media Types clause in the What To Look For? section of a content rule.
| Custom Media Type detection only applies to attachments that would otherwise have been classified as Unknown Binary. It cannot be used to override the built-in recognition for all the media types that are supported by the Gateways. |
Custom Media Type Signatures
Custom Media Types 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.
When adding a new signature:
- The Signature Pattern cannot be longer than the offset +1, if searching from the end of the file.
- The Signature Pattern must only contain valid hexadecimal values within the range of 0-255.
- Each byte in the Signature Pattern must be separated by a space.
- The value of the offset that the search will start from must be between 0 and 2147483647, where an offset of zero would search from the start or end of a file.
| We recommend that defined signatures should be as long as possible. Single byte sequences are not recommended. |
A Hex Editor can be used to identify a particular signature in a file. For further information, see this knowledge article on the Fortra Support Portal.