I just created my digitalocean account a few days ago, and I just found that there are a very big number of Root log in fail logged in my /var/log/secure. It shows 67374 lines in that file. For instance, I only logged in once today but it shows lots of logs in. The login attempts are performed by my own user. These are a few lines: 67366 Jul 3 22:33:59 lingvi sshd[28849]: Failed password for root from 43.255.188.145 port 55580 ssh2 67367 Jul 3 22:33:59 lingvi sshd[28849]: Received disconnect from 43.255.188.145: 11: [preauth] 67368 Jul 3 22:33:59 lingvi sshd[28849]: PAM 2 more authentication failures; logname= uid=0 euid=0 tty=ssh ruser= rhost=43.255.188.145 user=root 67369 Jul 3 22:33:59 lingvi sshd[28851]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=43.255.188.145 user=root 67370 Jul 3 22:33:59 lingvi sshd[28851]: pam_succeed_if(sshd:auth): requirement “uid >= 1000” not met by user “root” 67371 Jul 3 22:34:01 lingvi sshd[28851]: Failed password for root from 43.255.188.145 port 42254 ssh2 67372 Jul 3 22:34:01 lingvi sshd[28851]: pam_succeed_if(sshd:auth): requirement “uid >= 1000” not met by user “root” 67373 Jul 3 22:34:03 lingvi sshd[28851]: Failed password for root from 43.255.188.145 port 42254 ssh2 67374 Jul 3 22:34:04 lingvi sshd[28851]: pam_succeed_if(sshd:auth): requirement “uid >= 1000” not met by user “root” :set number
The logs are constantly increasing in an automated way. What could cause this?
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Hi, they’re attempts to login to SSH using brute-force attacks. Changing the port is not effective because an attacker can actually perform a port scan to see which service is listening on a given port. You can simply modify the SSH configuration file to block the root user, thus allowing only a user of your choice already added to the sudoers list. If attacks come from the same IP, you can block that IP with a simple rule of your firewall. If they come from a range of IPs, you can block that range as mentioned above. Usually this kind of intrusion attempts are all due to botnets, but they can also come from a single host. If you have a control panel on your droplet and you don’t use SSH regularly, you can disable it by stopping the associated service. This also applies to other services, such as FTP.
You can block the IP Address of the attacker using the UFW firewall for example: sudo ufw deny from <ip address>
However It would also be safe to follow some security measures that you’ll find In this article: https://www.digitalocean.com/community/tutorials/7-security-measures-to-protect-your-servers
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