Proftp 접속 후 메시지 발생하고 접속 종료 됩니다.

아래와 같이 접속 하면 서버에서 메세지 발생후 접속이 close 됩니다.

이유가 뭘까요?

궁금해서 올립니다.

FTP session requested from unknown class
connected - local : 210.123.46.4:21
connected - remote : 210.123.32.194:3730
FTP session opened.
dispatching PRE_CMD command 'USER stony15' to mod_core
dispatching PRE_CMD command 'USER stony15' to mod_core
dispatching PRE_CMD command 'USER stony15' to mod_auth
dispatching CMD command 'USER stony15' to mod_auth
dispatching LOG_CMD command 'USER stony15' to mod_log
dispatching PRE_CMD command 'PASS (hidden)' to mod_core
dispatching PRE_CMD command 'PASS (hidden)' to mod_core
dispatching PRE_CMD command 'PASS (hidden)' to mod_auth
dispatching CMD command 'PASS (hidden)' to mod_auth
PAM(stony15): Authentication failed.
USER stony15 (Login failed): Incorrect password.
dispatching LOG_CMD_ERR command 'PASS (hidden)' to mod_log
dispatching LOG_CMD_ERR command 'PASS (hidden)' to mod_auth
dispatching PRE_CMD command 'USER stony15' to mod_core
dispatching PRE_CMD command 'USER stony15' to mod_core
dispatching PRE_CMD command 'USER stony15' to mod_auth
dispatching CMD command 'USER stony15' to mod_auth
dispatching LOG_CMD command 'USER stony15' to mod_log
dispatching PRE_CMD command 'PASS (hidden)' to mod_core
dispatching PRE_CMD command 'PASS (hidden)' to mod_core
dispatching PRE_CMD command 'PASS (hidden)' to mod_auth
dispatching CMD command 'PASS (hidden)' to mod_auth
ProFTPD terminating (signal 11)
FTP session closed.