There are definitely some countries you should be blocking from accessing your site however, instead of blocking them outright, you should send to sites where you actually gain traffic or income from that traffic.

For example, signup to a toplist and send your 'blocked' traffic to that, in return, you should get some usable traffic back from the toplist... Another thing we do on our freesite domains is send it to some of our private TGPs that use hosted galleries.. That way, the traffic actually gets to see some porn, and we have a potential at making a sale via a sponsor hosted gallery and.. Best of all, we dont need to worry about hotlinking

If you are talking about these attempts being made on paysites you own, simply get StrongBox installed and dont have any worries as StrongBox will automatically block those IPs.

Regards,

Lee