change ssh port in linux in following steps, are you getting lot of bot flood traffic, high cpu usage due to default ssh port 22 in linux, then change the ssh port in linux and get sae server costs, and scale your linux server by simply changing the linux ssh port.
with default port 22
sshd Invalid user from port 33378
first allow New Port in linux firewall & cloud provide firewall
ex: my case added digitalocean firewall.
Check well known ports choose from (1024 to 65535)
add new SSH port to linux firewall allow list
edit openssh in ubuntu debian linux distro
Change default ssh port 22 to new port
#2 change ssh port in linux – restart sshd or ssh server – #
Check SSH server listening newport or not
Login with New Port – change ssh port in linux
Block Port 22 Using UFW Firewall – change ssh port in linux
WARN: Skipping ‘openssh-server‘: couldn’t process
Block Port 22 using digitalocean firewall
Check linux auth syslogs get rid of ddos attacks
Apr 24 06:26:44 -s-4vcpu-8gb-blr1-01 sudo: root : TTY=pts/0 ; PWD=/root ; US ER=root ; COMMAND=/usr/sbin/ufw deny 22
Failed password for invalid user dong from 170.245.200.100 port 54354 ssh2
Apr 18 06:27:44 -s-4vcpu-8gb-blr1-01 sshd[19631]: Received disconnect from 170.245.200.100 port 54354:11: Bye Bye [preauth]
Apr 18 06:27:44 -s-4vcpu-8gb-blr1-01 sshd[19631]: Disconnected from invalid user dong 170.245.200.100 port 54354 [preauth]
Apr 18 06:27:58 -s-4vcpu-8gb-blr1-01 sshd[19633]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=80.169.112.191 user=root
Apr 18 06:28:00 -s-4vcpu-8gb-blr1-01 sshd[19633]: Failed password for root from 80.169.112.191 port 33064 ssh2
Apr 18 06:28:01 -s-4vcpu-8gb-blr1-01 sshd[19633]: Received disconnect from 80.169.112.191 port 33064:11: Bye Bye [preauth]
Apr 18 06:28:01 -s-4vcpu-8gb-blr1-01 sshd[19633]: Disconnected from authenticating user root 80.169.112.191 port 33064 [preauth]
//disable root login, password login, pamuse=no.
Summary on changing ssh linux port
Hope, you get clear understanding of change of ssh port in linux, and the effects of changing linux ssh ports get rid bot traffic and strengthening linux server security you also want know about hardening linux security by tweaking sysctl. conf
