they only seem to try 1 account at a time and ONLY 1 attempt at that account , but the same IP number tries numerous different accounts. I can't see any way in CFS settings to block IPs that attempt to log in to different accounts, only settings for how many times the same account is attempted
/var/log/secure:
Mar 13 08:53:15 knight proftpd[18062]: 198.1.75.187 (199.114.243.224[199.114.243.224]) - USER co: no such user found from 199.114.243.224 [199.114.243.224] to ::ffff:198.1.75.187:21
Mar 13 08:53:25 knight proftpd[18091]: 198.1.75.187 (199.114.243.224[199.114.243.224]) - USER couk: no such user found from 199.114.243.224 [199.114.243.224] to ::ffff:198.1.75.187:21
Mar 13 08:53:34 knight proftpd[18150]: 198.1.75.187 (199.114.243.224[199.114.243.224]) - USER co111: no such user found from 199.114.243.224 [199.114.243.224] to ::ffff:198.1.75.187:21
Mar 13 08:53:37 knight proftpd[18170]: 198.1.75.187 (199.114.243.224[199.114.243.224]) - USER co123: no such user found from 199.114.243.224 [199.114.243.224] to ::ffff:198.1.75.187:21
Mar 13 08:53:40 knight proftpd[18203]: 198.1.75.187 (199.114.243.224[199.114.243.224]) - USER co123456: no such user found from 199.114.243.224 [199.114.243.224] to ::ffff:198.1.75.187:21
Mar 13 08:53:40 knight proftpd[18206]: 198.1.75.187 (199.114.243.224[199.114.243.224]) - USER co2010: no such user found from 199.114.243.224 [199.114.243.224] to ::ffff:198.1.75.187:21
Mar 13 08:53:43 knight proftpd[18228]: 198.1.75.187 (199.114.243.224[199.114.243.224]) - USER co2011: no such user found from 199.114.243.224 [199.114.243.224] to ::ffff:198.1.75.187:21
Mar 13 08:53:44 knight proftpd[18231]: 198.1.75.187 (199.114.243.224[199.114.243.224]) - USER co2012: no such user found from 199.114.243.224 [199.114.243.224] to ::ffff:198.1.75.187:21