beh, fino al 30 settembre il server funzionava a dovere, visto quello che ho trovato nei log....

Sep 30 00:37:47 localhost proftpd[7870]: localhost.localdomain (202.222.18.65[202.222.18.65]) - Maximum login attempts (3) exceeded
Sep 30 00:37:49 localhost proftpd[7871]: localhost.localdomain (202.222.18.65[202.222.18.65]) - USER test: no such user found from 202.222.18.65 [202.222.18.65] to 192.168.0.50:21
Sep 30 00:37:50 localhost last message repeated 2 times
Sep 30 00:37:50 localhost proftpd[7871]: localhost.localdomain (202.222.18.65[202.222.18.65]) - Maximum login attempts (3) exceeded
Sep 30 00:37:52 localhost proftpd[7872]: localhost.localdomain (202.222.18.65[202.222.18.65]) - USER test: no such user found from 202.222.18.65 [202.222.18.65] to 192.168.0.50:21
Sep 30 00:37:52 localhost proftpd[7872]: localhost.localdomain (202.222.18.65[202.222.18.65]) - USER test: no such user found from 202.222.18.65 [202.222.18.65] to 192.168.0.50:21
Sep 30 00:37:53 localhost proftpd[7872]: localhost.localdomain (202.222.18.65[202.222.18.65]) - SECURITY VIOLATION: root login attempted.
Sep 30 00:37:53 localhost proftpd[7872]: localhost.localdomain (202.222.18.65[202.222.18.65]) - Maximum login attempts (3) exceeded
Sep 30 00:37:55 localhost proftpd[7873]: localhost.localdomain (202.222.18.65[202.222.18.65]) - SECURITY VIOLATION: root login attempted.
Sep 30 00:37:56 localhost last message repeated 2 times