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About Custom Media Type Signatures

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.

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.

A Hex Editor can be used to identify a particular signature in a file. For further information, see knowledge base article #1161 "Custom Media Types using Fingerprint Utilities" on the Clearswift Support Portal.

Examples

These examples are based on the following hexadecimal strings at the start and end of a file:

84 2A 4B 3D 22............20 56 68 00 00 2A 17 4A 65

Example 1

To identify the value 4A one byte from the end of a file:

1. Enter 4A in the Signature Pattern field.
2. Select end of the file in the From field.
3. Enter 1 in the Offset field.

Example 2

To identify the value 20 56 68 00 00 2A 17 4A 65 nine bytes from the end of a file:

1. Enter 20 56 68 00 00 2A 17 4A 65 in the Signature Pattern field.
2. Select end of the file in the From field.
3. Enter 9 in the Offset field.

Example 3

To identify the value 84 2A 4B 3D 22 at the start of a file:

1. Enter 84 2A 4B 3D 22 in the Signature Pattern field.
2. Select start of the file in the From field.
3. Enter 0 in the Offset field.

Example 4

To identify the value 4B 3D 22 two bytes from the start of a file:

1. Enter 4B 3D 22 in the Signature Pattern field.
2. Select start of the file in the From field.
3. Enter 2 in the Offset field.

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