当通过SSH连接到我的Ubuntu 16.04服务器时，我的控制台被这样的消息污染：
root@backup ~ # 2017 May 2 15:05:05 backup fatal: Unable to negotiate with XXX port 45700: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1 [preauth] 2017 May 2 15:05:07 backup fatal: Unable to negotiate with XXX port 45991: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1 [preauth] 2017 May 2 15:05:07 backup fatal: Unable to negotiate with XXX port 45981: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1 [preauth] ... XXX是一个外国IP（不是我的，也不是我的服务器的IP）。 所以似乎有一个字典攻击的SSH服务，这是很常见的。 我怎样才能发送这些消息到日志文件，而不是让他们在控制台上？
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sshd_conf
# Package generated configuration file # See the sshd_config(5) manpage for details # What ports, IPs and protocols we listen for Port 22 # Use these options to restrict which interfaces/protocols sshd will bind to #ListenAddress :: #ListenAddress 0.0.0.0 Protocol 2 # HostKeys for protocol version 2 HostKey /etc/ssh/ssh_host_rsa_key HostKey /etc/ssh/ssh_host_dsa_key HostKey /etc/ssh/ssh_host_ecdsa_key #Privilege Separation is turned on for security UsePrivilegeSeparation yes # Lifetime and size of ephemeral version 1 server key KeyRegenerationInterval 3600 ServerKeyBits 768 # Logging SyslogFacility AUTH LogLevel INFO # Authentication: LoginGraceTime 120 PermitRootLogin without-password StrictModes yes RSAAuthentication yes PubkeyAuthentication yes #AuthorizedKeysFile %h/.ssh/authorized_keys # Don't read the user's ~/.rhosts and ~/.shosts files IgnoreRhosts yes # For this to work you will also need host keys in /etc/ssh_known_hosts RhostsRSAAuthentication no # similar for protocol version 2 HostbasedAuthentication no # Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication #IgnoreUserKnownHosts yes # To enable empty passwords, change to yes (NOT RECOMMENDED) PermitEmptyPasswords no # Change to yes to enable challenge-response passwords (beware issues with # some PAM modules and threads) ChallengeResponseAuthentication no # Change to no to disable tunnelled clear text passwords #PasswordAuthentication yes # Kerberos options #KerberosAuthentication no #KerberosGetAFSToken no #KerberosOrLocalPasswd yes #KerberosTicketCleanup yes # GSSAPI options #GSSAPIAuthentication no #GSSAPICleanupCredentials yes X11Forwarding yes X11DisplayOffset 10 PrintMotd no PrintLastLog yes TCPKeepAlive yes #UseLogin no #MaxStartups 10:30:60 #Banner /etc/issue.net # Allow client to pass locale environment variables AcceptEnv LANG LC_* Subsystem sftp /usr/lib/openssh/sftp-server # Set this to 'yes' to enable PAM authentication, account processing, # and session processing. If this is enabled, PAM authentication will # be allowed through the ChallengeResponseAuthentication and # PasswordAuthentication. Depending on your PAM configuration, # PAM authentication via ChallengeResponseAuthentication may bypass # the setting of "PermitRootLogin without-password". # If you just want the PAM account and session checks to run without # PAM authentication, then enable this but set PasswordAuthentication # and ChallengeResponseAuthentication to 'no'. UsePAM yes #Note that match is effective "until either another Match line or the end of the file." #(the indentation isn't significant) Match User rsnapshot PasswordAuthentication no
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root@backup ~ # sysctl -a | grep kernel.printk kernel.printk = 4 4 1 7 kernel.printk_delay = 0 kernel.printk_devkmsg = ratelimit kernel.printk_ratelimit = 5 kernel.printk_ratelimit_burst = 10 sysctl: reading key "net.ipv6.conf.all.stable_secret" sysctl: reading key "net.ipv6.conf.default.stable_secret" sysctl: reading key "net.ipv6.conf.eth0.stable_secret" sysctl: reading key "net.ipv6.conf.lo.stable_secret"