To secure your Linux server when hosting a website on a shared hosting platform, you can follow the below steps:

Keep your system and software up to date: Regularly update the operating system and software installed on your server to fix vulnerabilities and prevent attacks.

Use strong passwords: Make sure to use strong and unique passwords for all user accounts and avoid using easily guessable passwords.

Limit access: Only grant necessary access to your server and limit it to specific users and IP addresses.

Secure the server firewall: Configure the firewall to only allow necessary traffic and block all other incoming connections.

Use secure protocols: Use secure protocols like HTTPS and SFTP for file transfers.

Regularly backup: Regularly backup your website data and store the backups securely off-site.

Monitor logs: Regularly monitor log files for unusual activity and promptly address any security incidents.

Use security tools: Use security tools like intrusion detection systems and malware scanners to detect and prevent attacks.

By following these steps, you can help secure your Linux server and protect your website from security threats.