After you buy a Linux VPS, security starts on day one. Change default passwords immediately, create a sudo user, and prefer SSH keys over password login.
Enable a firewall (UFW or firewalld) and allow only the ports you need — typically SSH, HTTP/HTTPS, and your app ports. Keep the OS updated with unattended or scheduled patches.
Disable root SSH login where possible, use a non-default SSH port only as a minor speed bump (not a full defense), and install fail2ban or equivalent brute-force protection.
Turn on automatic backups or snapshots for critical data. Monitor disk, CPU, and auth logs so you catch issues before customers do.
LinuxPro servers include reinstall options from the panel if you need a clean OS after a compromise — but prevention is always cheaper than recovery.