blocking people from nigeria and senegal

i am running a jobsite which is india specific, but nigerian scammers, register as  employers/members, send fake emails to members, and try to scam them , by fooling them for money in return of job
so iam trying to block them
i got this tutorial
http://www.hosting.com/support/dedicated/IIS/blockip/
and blocked the senegal ip address inetnum
there isp itself
i blocked using group of computers ,entering these ipaddress     41.214.0.0 - 41.214.127.255


have i done it all right?
becoz i want to block more ipaddresses


thanks

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