dropbear[31615]: login attempt for nonexistent user from

Hi, today I was checking the router's System Log and found the following messages, is it possible that somebody is trying to hack the router? I do not have WAN access enabled, but I did have SSH enabled, now I have changed SSH to LAN Only. Any other suggestion to secure the router against these type of attacks? thanks

Apr 1 18:50:17 dropbear[31615]: login attempt for nonexistent user from ::ffff:103.231.211.250:34800
Apr 1 18:50:20 dropbear[31616]: login attempt for nonexistent user from...

dropbear[31615]: login attempt for nonexistent user from