valid_referers

Specifies the “Referer” request header field values that will cause the embedded $invalid_referer variable to be set to an empty string. Otherwise, the variable will be set to “1”. Search for a match is case-insensitive.

Parameters can be as follows:

none

the “Referer” field is missing in the request header;

blocked

the “Referer” field is present in the request header, but its value has been deleted by a firewall or proxy server; such values are strings that do not start with “http://” or “https://”;

server_names

the “Referer” request header field contains one of the server names;

arbitrary string

defines a server name and an optional URI prefix. A server name can have an “*” at the beginning or end. During the checking, the server’s port in the “Referer” field is ignored;

regular expression

the first symbol should be a “~”. It should be noted that an expression will be matched against the text starting after the “http://” or “https://”.

Example:

valid_referers none blocked server_names
               *.example.com example.* www.example.org/galleries/
               ~\.google\.;