Common threats
These are some common threats people face when they're thinking about defending their privacy and security. You may be concerned with none, one, a few, or all of these possibilities, and the plan you make depends on what your individual goals are.
5. Targeted attacks
Targeted attacks against a specific person are more problematic to deal with. Common attacks include sending malicious documents via email, exploiting vulnerabilities (e.g. in browsers and operating systems), and physical attacks. If this is a concern for you, you should employ more advanced threat mitigation strategies.
If you are concerned about physical attacks you should use an operating system with a secure verified boot implementation, such as Android, iOS, macOS, or Windows (with TPM). You should also make sure that your drive is encrypted, and that the operating system uses a TPM or Secure Enclave/Element to rate limit attempts to enter the encryption passphrase. You should avoid sharing your computer with people you don't trust, because most desktop operating systems don't encrypt data separately per-user.