Introduction to LineageOS 21 on Pixel 8 and the Need for Hardening

Installing a custom ROM like LineageOS 21 on your Pixel 8 is a powerful step towards regaining control over your device and enhancing your privacy. While LineageOS offers a significant privacy uplift compared to stock Android with Google services, the initial installation is just the beginning. To truly secure your device and maximize its privacy potential, a series of post-installation hardening steps and advanced configuration tweaks are essential. This guide will walk you through expert-level modifications to fortify your Pixel 8 running LineageOS 21, ensuring a robust and private mobile experience.

These steps assume you have successfully installed LineageOS 21 on your Pixel 8, ideally without GApps, and are familiar with basic Android settings and ADB commands. Our focus will be on minimizing data leakage, restricting unwanted connections, and leveraging LineageOS’s built-in privacy features alongside recommended third-party tools.

Foundational Security Checks

Before diving into advanced tweaks, let’s verify some fundamental security aspects of your LineageOS installation.

Verify Encryption Status

Modern Android devices, including the Pixel 8, are designed for File-Based Encryption (FBE) by default. LineageOS maintains this critical security feature. It’s crucial to confirm your device is encrypted to protect your data at rest.

• Navigate to Settings > Security & privacy > Encryption & credentials.
• Under ‘Encryption’, you should see ‘Phone encrypted’. If it’s not encrypted, you must factory reset your device, as encryption typically occurs during the initial setup process.

SELinux Status Verification

SELinux (Security-Enhanced Linux) is a mandatory access control system that adds an extra layer of security. It must be in ‘Enforcing’ mode for optimal protection against privilege escalation attacks and malicious apps.

To check SELinux status, open a terminal app on your device (e.g., Termux from F-Droid) or use ADB from your computer:

adb shell getenforce

The output should be Enforcing. If it reports ‘Permissive’ or ‘Disabled’, your device’s security posture is severely weakened. This usually indicates a problem with the ROM installation or a modified kernel, and it’s highly recommended to resolve it by reinstalling LineageOS or checking for a patched kernel.

Essential System Tweaks for Enhanced Privacy

Enabling Developer Options and Advanced Reboot

Developer options unlock many powerful settings necessary for advanced hardening, including ADB access and custom quick settings tiles.

• Go to Settings > About phone.
• Tap ‘Build number’ seven times until ‘You are now a developer!’ appears.
• Return to Settings > System > Developer options.
• Enable ‘Advanced reboot’ (Power menu > Reboot > Recovery/Bootloader). This is helpful for system maintenance.

Disabling Unnecessary Features

Minimize your digital footprint by disabling features you don’t actively use.

• Wi-Fi and Bluetooth Scanning: Even when Wi-Fi and Bluetooth are off, your device can still scan for networks and devices for location accuracy.
• Navigate to Settings > Location > Location services.
• Toggle off ‘Wi-Fi scanning’ and ‘Bluetooth scanning’.
• Personalized Ads: Disable ad personalization where possible within app settings. For LineageOS without GApps, this is less relevant, but good practice.
• Location Accuracy: Consider disabling Google Location Accuracy (if microG is installed) or similar services if you rely purely on GPS.

Fine-tuning App Permissions with Privacy Guard

LineageOS’s Privacy Guard (or similar permission manager in LineageOS 21) allows granular control over what apps can access. This is a cornerstone of device hardening.

• Go to Settings > Security & privacy > Privacy > Permission manager.
• Review permissions like ‘Location’, ‘Camera’, ‘Microphone’, ‘Contacts’, ‘SMS’, ‘Call logs’, and ‘Files and media’.
• For each permission, examine which apps have access. Revoke permissions for any app that doesn’t strictly require it for its core functionality. Pay special attention to system apps as well.
• Alternatively, you can manage permissions per app by going to Settings > Apps > See all apps > [App Name] > Permissions.

Network and DNS Hardening

Your network traffic is a prime target for surveillance. Hardening your network configuration is crucial.

Custom DNS Configuration

Using a private DNS provider encrypts your DNS queries and can block ads and trackers at the network level.

• Go to Settings > Network & internet > Private DNS.
• Select ‘Private DNS provider hostname’.
• Enter a provider hostname. Recommended options include:
  • dns.cloudflare-dns.com (Cloudflare DNS)
  • dns.adguard.com (AdGuard DNS – blocks ads/trackers)
  • dot.libredns.gr (LibreDNS – privacy-focused)
• Tap ‘Save’.

Implementing a System-Wide Firewall (e.g., RethinkDNS)

A local VPN-based firewall gives you unparalleled control over app network access, allowing you to block internet access for specific apps or even specific domains.

• Install RethinkDNS + Firewall: Obtain it from F-Droid.
• Open RethinkDNS and follow the initial setup.
• Configure Firewall Rules:
  • Access the ‘Apps’ tab to block internet access (Wi-Fi, Mobile Data) for individual apps.
  • Utilize the ‘DNS’ tab to enable blocklists for ads, malware, and trackers.
  • Explore the ‘Firewall’ rules to block specific IP addresses or domains.
• Keep it running in the background to enforce your rules.

Advanced Privacy Applications and Best Practices

Managing Applications with F-Droid and Aurora Store

When you’ve opted for a GApps-free LineageOS installation, F-Droid becomes your primary app source for free and open-source software (FOSS). For proprietary apps that aren’t on F-Droid, Aurora Store is your go-to.

• F-Droid: Install F-Droid from their official website. Regularly update app repositories and apps.
• Aurora Store: Install Aurora Store via F-Droid. Use the ‘Anonymous’ login method to download apps from Google Play without associating them with a Google account.

Application Isolation with Shelter

Shelter leverages Android’s ‘Work Profile’ feature to isolate apps, preventing them from accessing your personal data or other apps outside their profile. This is ideal for social media apps, proprietary tools, or any app you don’t fully trust.

• Install Shelter: Get it from F-Droid.
• Follow the setup to create a work profile.
• Clone apps into the work profile or install new apps directly into it.
• Apps in the work profile are marked with a briefcase icon and run in an isolated environment.

Browser Hardening

Your web browser is a major vector for tracking.

• Recommended Browsers:
  • Bromite: A Chromium fork with enhanced privacy and security features, including ad blocking. Available from its official website or F-Droid via custom repo.
  • Firefox Focus: A privacy-focused browser that automatically blocks trackers and clears browsing history.
  • Brave Browser: Blocks ads and trackers by default.
• Browser Add-ons (for Firefox-based browsers): Install uBlock Origin to further enhance ad and tracker blocking.

Physical Security and Lock Screen Enhancements

The best software security can be undone by poor physical security.

Strong Authentication Methods

• Use a Strong PIN or Password: A 6-digit PIN is the minimum, but an alphanumeric password offers superior security. Avoid patterns, which are easily guessable.
• Go to Settings > Security & privacy > Device unlock.
• Configure a strong password or PIN.

Disabling Smart Lock and Trusted Agents

While convenient, features like Smart Lock (which keeps your phone unlocked in trusted locations or with trusted devices) and other Trusted Agents reduce your device’s security posture.

• Go to Settings > Security & privacy > Device unlock > Smart Lock.
• Enter your PIN/password and disable all Smart Lock options (On-body detection, Trusted places, Trusted devices, etc.).
• Go to Settings > Security & privacy > More security & privacy > Trust agents and ensure only ‘Smart Lock (Google)’ (if microG is present) or ‘None’ is enabled.

Staying Updated and Maintaining Security

Regular System Updates

LineageOS releases monthly security updates and regular feature enhancements. Promptly applying these updates is critical.

• Go to Settings > System > Updater.
• Regularly check for and install updates. Always ensure your device is sufficiently charged or connected to power before initiating an update.

Verifying Updates and Signatures

LineageOS updates are cryptographically signed. The built-in updater verifies these signatures automatically, ensuring the integrity and authenticity of the updates. Trust this process.

Conclusion

By diligently implementing these post-installation hardening steps, you transform your Pixel 8 running LineageOS 21 into a truly private and secure mobile powerhouse. From granular app permission control and network-wide ad blocking to physical security enhancements, each tweak contributes to a robust defense against surveillance and data exploitation. Remember that security is an ongoing process; stay vigilant, keep your system updated, and regularly review your privacy settings to maintain an impenetrable digital sanctuary.