What are the top security measures for hardening an operating system in a high-risk environment?

2 Configure user accounts and permissions

Another key security measure for hardening an OS is to configure the user accounts and permissions on your system. You should create separate accounts for different users and roles, and assign them the minimum privileges and access rights they need to perform their tasks. You should also disable or delete any unused or default accounts, and change any default passwords. You should enforce strong password policies, such as requiring complex and unique passwords, and expiring them after a certain period. You should also enable multi-factor authentication (MFA) for any remote or administrative access to your system.

3 Implement firewall and antivirus

A firewall is a software or hardware device that filters and controls the incoming and outgoing network traffic on your system. A firewall can help you block or allow specific ports, protocols, applications, and IP addresses, and prevent unauthorized or malicious connections. You should enable and configure your OS's built-in firewall, or use a third-party firewall solution, and customize the rules according to your network environment and security needs. You should also install and update an antivirus software on your system, and scan your files and folders regularly for any malware or viruses.

4 Encrypt data and communication

Encrypting your data and communication is another essential security measure for hardening an OS in a high-risk environment. Encryption is the process of transforming your data into an unreadable form that can only be decrypted with a key or a password. Encryption can protect your data from being stolen, tampered, or intercepted by unauthorized parties. You should encrypt your hard drive or partitions, your removable media, your backups, and your cloud storage with a strong encryption algorithm and key. You should also encrypt your network communication, such as your email, web browsing, and file transfers, with a secure protocol, such as HTTPS, SSL, or VPN.

6 Harden specific services and applications

The last security measure for hardening an OS in a high-risk environment is to harden the specific services and applications that run on your system. Depending on your OS and your use case, you may have different services and applications that require additional security settings and configurations. For example, you may need to harden your web server, your database server, your SSH server, or your email server, by disabling unnecessary features, restricting access, enforcing encryption, and applying best practices. You should also harden your web browser, your email client, your office suite, and any other applications that you use frequently, by updating them, configuring them, and using them securely.