My Ubuntu server had recently problems with a bruteforce attack.So I installed fail2ban and I think the problem is gone.But when I check iftop I see a Chinese IP permanently connecting.iftop                12.5Kb          25.0Kb          37.5Kb          50.0Kb    62.5KbmqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqUbuntu-1510-wily-64-minim  => 218.201.37.134             4.22Kb  4.12Kb  4.13Kb                           <=                            6.33Kb  6.19Kb  6.20KbqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqTX:             cum:    205KB   peak:   7.10Kb  rates:   5.38Kb  5.12Kb  5.32KbRX:                     233KB           8.37Kb           6.48Kb  6.34Kb  6.46KbTOTAL:                  438KB           15.5Kb           11.9Kb  11.5Kb  11.8KbIs this normal or do I have a problem.There is only Teamspeak an Minecraft running on the server.edit1:lsof -i -nCOMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAMEsshd       656 root    3u  IPv4  16856      0t0  TCP *:ssh (LISTEN)sshd       656 root    4u  IPv6  16858      0t0  TCP *:ssh (LISTEN)ts3server  898 root   32u  IPv4  17853      0t0  TCP *:30033 (LISTEN)ts3server  898 root   33u  IPv6  17854      0t0  TCP *:30033 (LISTEN)ts3server  898 root   34u  IPv4  16985      0t0  UDP myip:34773->194.97.114.3:2010ts3server  898 root   39u  IPv4  17862      0t0  UDP *:9987ts3server  898 root   40u  IPv6  17863      0t0  UDP *:9987ts3server  898 root   45u  IPv4  17867      0t0  TCP *:10011 (LISTEN)ts3server  898 root   46u  IPv6  17868      0t0  TCP *:10011 (LISTEN)java      1050 root   46u  IPv6  20495      0t0  TCP *:25565 (LISTEN)sshd      1220 root    3u  IPv4  21663      0t0  TCP *:1022 (LISTEN)sshd      1220 root    4u  IPv6  21665      0t0  TCP *:1022 (LISTEN)sshd      4347 root    3u  IPv4  55148      0t0  TCP myip:ssh->mysship:50031 (ESTABLISHED)There are no logins (checked via last) that are not from me.
Permanent connection to a chinese ip
ubuntu;security;iftop