Usually they will search for formmail in /cgi-bin/ on my users sites and the return statis is a 404 page not found. Then they go to /cgi-sys/ and do the same thing. Now if you look up these ips on the RBL lists you will find that most of them are blacklisted with more then one RBL.
So with that said, i dont mind posting their ips in public, which i dont normally do, but if they are going to hit my system on a daily basis it serves them right.
NOTE: I found alot of these ips hitting not just one server by more then 1 that own.
200.246.46.131 <--- The worst one
216.228.192.43
64.107.124.98
200.230.113.4
62.235.237.144
218.145.25.112
209.52.50.3
203.114.169.19
12.220.37.38
194.206.1.42
62.211.58.43
211.20.131.242
208.181.21.195
210.404.41.13
64.180.138.174
207.44.218.96
-EOF