Blocking based on proxy_add_x_forwarded_for

[Shri @ DevLib.Org]

I have a situation where a fair number of spammers are sneaking in through proxy servers.

Their real IP addresses can be traced back and identified.

Our current blocking works like this.

        location / {
              deny A.B.0.0/16;
        }

Is there any way possible where I could check the $proxy_add_x_forwarded_for address and block these spammers on our forums?

Regards,
Shri
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