sshd[xxx]: Bad protocol version identification 'XX' from a.b.c.d メッセージまたは Did not receive identification string from a.b.c.d メッセージが /var/log/secure に出力される

Issue

messages ログに、以下のようなエントリーが含まれます。

Mar 12 22:31:14 hostname sshd[772]:Did not receive identification string from a.b.c.d
Mar 12 22:31:14 hostname sshd[820]:Did not receive identification string from a.b.c.d
Mar 12 22:33:38 hostname vsftpd(pam_unix)[855]: check pass; user unknown
Mar 12 22:33:38 hostname vsftpd(pam_unix)[855]: authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=a.b.c.d 
Mar 12 22:33:40 hostname sshd[857]:Did not receive identification string from a.b.c.d
Mar 12 22:33:40 hostname sshd[858]:Address a.b.c.d maps to station.example.com, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
Mar 12 22:33:40 hostname vsftpd(pam_unix)[855]: check pass; user unknown
Mar 12 22:33:40 hostname vsftpd(pam_unix)[855]: authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=a.b.c.d 
Mar 12 22:33:43 hostname vsftpd(pam_unix)[860]: check pass; user unknown
Mar 12 22:33:43 hostname vsftpd(pam_unix)[860]: authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=a.b.c.d 
Mar 12 22:33:45 hostname vsftpd(pam_unix)[860]: check pass; user unknown
Mar 12 22:33:45 hostname vsftpd(pam_unix)[860]: authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=a.b.c.d 
....
Mar 12 22:35:07 hostname sshd[954]:Bad protocol version identification 'id' from a.b.c.d
Mar 12 22:35:28 hostname sshd[999]:Did not receive identification string from a.b.c.d
Mar 12 22:35:45 hostname sshd[1002]:Did not receive identification string from a.b.c.d
Mar 12 22:35:49 hostname sshd[1003]:Did not receive identification string from a.b.c.d
Mar 12 22:36:01 hostname sshd[1013]:Did not receive identification string from a.b.c.d
Mar 12 22:38:29 hostname sshd[15088]:Bad protocol version identification 'GET / HTTP/1.0' from 192.168.122.1