Below is a practical, OS-by-OS guide plus general best practices you can apply to protect personal data on desktops, laptops, phones, and tablets.

High-level principles (apply everywhere)

• Keep software updated: OS, apps, firmware, drivers — updates frequently patch security flaws.
• Use strong authentication: unique strong passwords, passphrases, and a password manager.
• Multi-factor authentication (MFA): enable for online accounts and any local accounts that support it.
• Minimize attack surface: remove unused apps, disable services you don’t need, avoid installing untrusted software.
• Principle of least privilege: run daily tasks as a limited user, not as admin/root.
• Backup regularly and test restores: keep at least one offline or encrypted off-site backup.
• Encrypt data at rest and in transit: use full-disk/file encryption and TLS/VPN for untrusted networks.
• Secure physical access: lock screens, use firmware passwords, and protect recovery keys.
• Be cautious with links and attachments (phishing) and with public Wi‑Fi.

Windows (11 / 10)

• Full-disk encryption:
  • Enable BitLocker (Pro/Enterprise/Education). If device has TPM, enable BitLocker and store the recovery key securely (print, USB, or cloud store if you accept the risk).
  • On Home editions, use device encryption (if available) or third-party full-disk tools.
• Account & credentials:
  • Use a Microsoft account with MFA or a local account plus a strong password and PIN.
  • Turn on Windows Hello (biometrics) if available.
• Secure Boot & TPM:
  • Keep Secure Boot enabled in UEFI; use TPM for BitLocker and credential protection.
• Patch & anti-malware:
  • Keep Windows Update on; use Windows Defender (built-in) or a reputable AV.
• App sources & permissions:
  • Install apps from Microsoft Store or trusted vendors. Use SmartScreen to block untrusted downloads.
• Network & firewall:
  • Keep Windows Firewall enabled; use VPN on public Wi‑Fi.
• File-level protection:
  • Use Encrypted File System (EFS) for per-file encryption if needed (Pro).
• Browser privacy:
  • Use strong privacy settings, disable unnecessary extensions, clear cookies, and consider containerized browser profiles.
• Secure deletion:
  • Use tools that overwrite free space if you need to permanently remove sensitive files.

macOS

• Full-disk encryption:
  • Enable FileVault (System Settings > Privacy & Security > FileVault). Save the recovery key in iCloud or print/store securely.
• Accounts & authentication:
  • Use an Admin account for installs and a standard account for daily use. Enable Touch ID/Apple Watch unlock if available.
• Secure Boot & T2 / Secure Enclave:
  • Keep Secure Boot settings and firmware password as appropriate; newer Macs use a Secure Enclave for keys.
• Gatekeeper & app sources:
  • Allow apps from App Store and identified developers; keep Gatekeeper enabled.
• Updates & malware:
  • Keep macOS and apps updated. Use XProtect and consider third-party malware tools for added protection.
• Network:
  • Use firewall (System Preferences), enable stealth mode, use VPN on untrusted networks.
• Privacy controls:
  • Review System Settings > Privacy & Security to control app access to files, microphone, camera, location.
• Secure deletion:
  • Use encrypted volumes (APFS encrypted disk images) and securely erase backups before disposal.

Linux (desktop/server)

• Full-disk encryption:
  • Use LUKS/dm-crypt at install time for root and home partitions. Example: cryptsetup luksFormat /dev/sdX and luksOpen.
• Boot & kernel security:
  • Use Secure Boot where supported; sign kernel modules if required.
• User accounts & privileges:
  • Use non-root daily user; use sudo for administrative tasks and limit sudoers.
• Mandatory access control:
  • Enable SELinux (Fedora/RHEL) or AppArmor (Ubuntu) and configure policies for critical services.
• Patch & package sources:
  • Use official repositories, enable unattended-upgrades for security patches on desktops/servers.
• Services & ports:
  • Disable unused services, use iptables/nftables and firewalld/ufw to restrict network access.
• File permissions & encryption:
  • Use appropriate POSIX permissions; consider eCryptfs or per-file GPG encryption for sensitive files.
• Backups:
  • Use rsync/duplicity/borg with encryption for remote backups.

Android

• Device encryption:
  • Most modern Android devices are encrypted by default. Ensure encryption is on (Settings > Security).
• Lock screen:
  • Use a strong PIN, password, or biometric with fallback disabled if possible. Set short auto-lock timeout.
• App sources:
  • Install only from Google Play Store or trusted sources. Disable “Install unknown apps.”
• App permissions:
  • Review and limit app permissions (location, storage, microphone, etc.). Revoke permissions you don’t need.
• Updates:
  • Keep OS and apps updated. Enable Play Protect.
• Google account & backups:
  • Use MFA on Google account; review backup settings for what’s synced.
• Sandboxing & isolation:
  • Use work profile (Android Enterprise) or separate user for two personas; use Scoped Storage-aware apps.
• Network:
  • Use VPN on public Wi‑Fi; disable auto-connect to open networks.
• Secure deletion:
  • Factory reset before disposing, and encrypt before reset if you want stronger protection.

iOS / iPadOS

• Device encryption:
  • iOS devices are encrypted by default when locked with a passcode.
• Lock screen:
  • Use a strong passcode (longer numeric or alphanumeric) and enable Face ID/Touch ID.
• App sources:
  • Only install from App Store. Use App Store settings and Screen Time to restrict installs if needed.
• App permissions & privacy:
  • Review app permissions in Settings (location, photos, microphone). Use per-app tracking controls and Privacy Report.
• Updates:
  • Keep iOS and apps updated; enable automatic updates.
• Apple ID & iCloud:
  • Enable MFA on Apple ID, review iCloud backup settings and what’s synced to iCloud.
• Network:
  • Use VPN on untrusted networks and Wi‑Fi privacy features (private address).
• Secure deletion:
  • Erase all content and settings before transfer; remove from iCloud and Activation Lock.

Email, Browsing, and Messaging (cross-platform)

• Use end-to-end encrypted messaging (Signal, iMessage, WhatsApp with verification) for sensitive conversations.
• Use secure email practices: avoid sending highly sensitive data via plain email, consider PGP/GPG for end-to-end email encryption where needed.
• Browser protections: enable HTTPS-Only, use uBlock/Privacy Badger, limit extensions, use private Windows for sensitive sessions.
• Password manager: use a reputable password manager cross-device; enable MFA for the vault.

Backups, Key management, and Recovery

• Backups:
  • Keep at least three copies (device, local encrypted backup, off-site encrypted backup).
  • Encrypt your backups and keep recovery keys separate from backups.
• Recovery keys:
  • Store recovery keys/passwords in a secure place (hardware security module, safe deposit box, or printed locked with physical security).
• Hardware security:
  • Consider using a hardware security key (FIDO2) for MFA; use USB/NFC keys for account protection.
• For enterprise or high-risk: use HSMs, secure enclaves, or enterprise mobile management (MDM) solutions.

Secure disposal and device transfer

• Full wipe:
  • Use full-disk encryption before wiping; then factory reset or use secure erase tools for HDDs (multiple overwrite) and cryptographic erase for SSDs.
• Remove accounts and disable activation locks:
  • On Apple, sign out of Apple ID and remove Activation Lock. On Android, remove Google account.
• Physically destroy drives if extremely sensitive.

Quick actionable checklist (short)

• Enable full-disk encryption (BitLocker/FileVault/LUKS/Android/iOS default).
• Lock device with strong passcodes and enable MFA for accounts.
• Keep OS/apps/firmware updated automatically.
• Use a password manager and enable MFA.
• Backup regularly and encrypt backups.
• Install apps only from trusted sources and review app permissions.
• Use firewall, anti-malware, and VPN on untrusted networks.
• Securely store recovery keys and wipe devices before disposal.

If you want, tell me which operating system(s) and device types you use and I’ll give a concise, step-by-step configuration list (including exact menu paths or commands) tailored to that environment.