Chapter 15 Unified Threat Management for FortiOS 5.0 : Custom Application & IPS Signatures : Custom signature keywords : Content keywords : depth
  
depth
Syntax: --depth <depth_int>;
Description:
Use the depth keyword to search for the contents within the specified number of bytes after the starting point defined by the offset keyword. If no offset is specified, the offset is assumed to be equal to 0.
If the value of the depth keyword is smaller than the length of the value of the content keyword, this signature will never be matched.
The depth must be between 0 and 65535.