How to secure a server against cyberattacks in 2025

Server security is a crucial aspect in today’s digital era, where hacking threats and data theft are increasingly frequent. Businesses and individuals who hold sensitive information on their servers must take concrete measures to protect them against malicious attacks. In this article, we will explore the different steps to secure a server and prevent security vulnerabilities.

The Importance of server security

Servers often contain confidential information, such as customer data, financial information, and trade secrets. If this data falls into the hands of hackers or malicious competitors, it can have catastrophic consequences for the business or individual concerned. Hackers can use this information to commit crimes, such as identity theft, account impersonation, or extortion. It is therefore essential to take measures to secure servers and protect the sensitive data stored on them.

Whether you have a dedicated server, a VPS, or a shared server with a hosting provider, security remains paramount. Linux servers like Ubuntu, Debian, CentOS, or Red Hat Enterprise Linux require special attention, as do Windows Server or virtual environments.

Establish a strong password policy

A strong password policy is one of the first elements to implement to secure a server. Passwords must be complex and difficult to guess, and it is recommended to change them regularly. Users should also avoid using the same passwords for multiple accounts, as this increases the risk of compromise in case of a security breach.

It is particularly important to secure the root user account and administrator accounts. Your password should contain at least 12 characters with a combination of letters, numbers, and symbols. It is also important to implement two-factor authentication, which requires additional verification before allowing access to the server. This measure adds an extra layer of security and makes unauthorized access to the server more difficult.

For Linux systems, using sudo instead of connecting directly as root is a recommended practice. This allows limiting privileges and tracing administrative actions.

Secure the website with HTTPS

The HTTPS (Hypertext Transfer Protocol Secure) protocol is a secure version of the HTTP protocol. It uses the SSL/TLS (Secure Sockets Layer/Transport Layer Security) protocol to encrypt data exchanged between the server and the client. This means that sensitive information, such as credit card numbers or passwords, is protected against interception and unauthorized reading.

It is therefore essential to configure the server to use the HTTPS protocol and obtain valid SSL certificates. Whether you use Apache, Nginx, or IIS as a web server, HTTPS configuration is essential. This not only improves the security of your website but also user trust and search engine rankings like Google Chrome and Mozilla Firefox.

SSL certificates also encrypt communications and verify the authenticity of your domain name. This security is particularly important for e-commerce sites and web applications that handle sensitive data.

Regularly ppdate the server

Regular server updates are crucial for maintaining system security and stability. Updates often bring security patches for known vulnerabilities, as well as performance and functionality improvements. It is important to update not only the operating system but also the software and applications installed on the server.

For Linux servers, use appropriate package managers (apt for Ubuntu/Debian, yum for CentOS/Red Hat) to keep your distributions up to date. Plugins and themes used by web applications, such as WordPress or PrestaShop, should also be updated regularly to avoid security vulnerabilities.

Environments like LAMP (Linux, Apache, MySQL, PHP) or WAMP (Windows, Apache, MySQL, PHP) require special attention. Also remember to update your MySQL or MariaDB databases, as well as PHP modules and frameworks used. Regular updates are an important administrative task that must be planned and executed regularly.

Disable unnecessary services and open ports

Unnecessary services and open ports can constitute significant security vulnerabilities if they are not properly configured. Services that are not necessary for server operation should be disabled or removed to reduce the attack surface. Similarly, open ports that are not used by applications should be closed to prevent unauthorized access.

On a Linux server, use commands like netstat or ss to identify running services. Disable unnecessary services like Telnet, unsecured FTP, or obsolete protocols. For example, if you don’t use an FTP server, disable this service. Similarly, close unnecessary TCP ports and properly configure network protocols.

Managing services and ports is an important task that requires a good understanding of how the server and installed applications work. It is also important to monitor connection logs to detect unauthorized access attempts and take measures to prevent them. Use monitoring tools to monitor your remote server activity.

Install malware analysis software

Malware, such as viruses, worms, and Trojans, can cause significant damage to the server and the data stored on it. It is therefore important to install malware analysis software to detect and eliminate these threats. A powerful antivirus is essential to protect your infrastructure.

Malware can infiltrate through different vectors: infected emails, compromised websites, or malicious scripts. Malware analysis software can be configured to perform regular scans of the server and files stored on it. They can also be configured to take automatic measures to eliminate detected malware.

It is important to choose malware analysis software that is compatible with the operating system and applications installed on the server. For Linux servers, solutions like ClamAV are available, while Windows servers can use Windows Defender or third-party solutions.

Install a firewall

A firewall is software or hardware that controls server access and blocks unauthorized connections. It is essential to install a firewall to protect the server against malicious attacks and unauthorized access attempts.

On Linux systems, iptables is the reference tool for configuring the firewall. You can also use UFW (Uncomplicated Firewall) on Ubuntu for simplified configuration. Firewalls can be configured to allow or block access based on predefined rules based on IP addresses, ports, or protocols.

A well-configured firewall should only allow necessary traffic. For example, allow port 80 for HTTP, port 443 for HTTPS, and the custom SSH port you configured. Block all other ports by default. It is important to properly configure rules for your local network (LAN) and remote connections.

Secure the server against brute force attacks

Brute force attacks are a technique used by hackers to try to guess passwords or encryption keys. It is important to take measures to secure the server against these types of attacks. Users should choose complex passwords that are difficult to guess, and it is recommended to change them regularly.

Administrators should also implement measures to limit connection attempts, such as timeouts between attempts or IP address blocking. Tools like Fail2Ban can automatically block IP addresses that attempt repeated failed connections.

It is also important to monitor connection logs to detect brute force attack attempts and take measures to prevent them. Configure appropriate logging to trace all SSH, FTP, or other critical service connection attempts.

Change the SSH port

The default SSH port (port 22) is often targeted by automated attacks. It is recommended to change the SSH port to prevent default attacks. Hackers may try to connect to the server using the default SSH port, so it is important to change it to a non-standard port.

To change the SSH port, modify the /etc/ssh/sshd_config configuration file on Linux systems, or use the graphical interface on Windows Server. Choose a port between 1024 and 65535 that is not used by other services. It is also important to configure the firewall to allow SSH connections only on the new port.

After modifying the server configuration, restart the SSH service with the appropriate command (sudo service ssh restart or sudo systemctl restart ssh). It is important to document the new port so that authorized users can connect to the server using the correct configuration.

Use public key authentication for SSH

Public key authentication is a secure connection method that uses a key pair to authenticate the user. It is recommended to use public key authentication for SSH connections, as it is more secure than traditional passwords.

Users must generate a key pair (public and private) and install the public key on the server. The private key must be kept secure and should not be shared with anyone. You can use tools like ssh-keygen on Linux/macOS or PuTTY on Windows to generate keys.

It is important to configure the server to use public key authentication and disable password authentication in the SSH configuration file. This method provides a higher level of security and facilitates automated connections via scripts.

Additional security measures

Data backup and integrity

Implement a regular backup system for your critical data. Whether you use a file server, a SQL Server database, or a mail server, backups are essential. Configure automatic backups to a remote server or secure storage system.

Monitoring and surveillance

Use monitoring tools to monitor your server activity in real-time. Solutions like Nagios, Zabbix, or cloud tools allow you to quickly detect anomalies and intrusion attempts.

Secure service configuration

If you use services like Apache2, Nginx, MySQL/MariaDB, or PHP, make sure they are properly configured. Modify default configuration files, remove default accounts (like admin/admin), and configure appropriate permissions on sensitive directories.

Certificate management and encryption

Use SSL/TLS certificates for all web services and secure connections. Configure encryption for server-to-server communications and enable secure protocols like SFTP instead of standard FTP.

Virtualization and isolation

If you use virtual environments or containers, ensure they are properly isolated. Virtualization can add an additional layer of security by separating applications and services.

In conclusion, securing a server is an ongoing process that requires constant attention and regular updates. By following these recommendations and adapting security measures to your specific environment (Linux server, Windows, or cloud solutions), you can significantly reduce attack risks and protect your sensitive data.

Remember that security is a balance between protection and functionality. Regularly consult security guides for your Linux distribution or hosting provider to stay informed about the latest threats and best practices. Continuous training and technology monitoring are essential to maintain an optimal security level.