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macOS Overview

macOS is a Unix operating system developed by Apple for their Mac computers. To enhance privacy on macOS, you can disable telemetry features and harden existing privacy and security settings.

Older Intel-based Macs and Hackintoshes do not support all the security features that macOS offers. To enhance data security, we recommend using a newer Mac with Apple silicon.

Privacy Notes

There are a few notable privacy concerns with macOS that you should consider. These pertain to the operating system itself, and not Apple's other apps and services.

Activation Lock

Brand new Apple silicon devices can be set up without an internet connection. However, recovering or resetting your Mac will require an internet connection to Apple's servers to check against the Activation Lock database of lost or stolen devices.

App Revocation Checks

macOS performs online checks when you open an app to verify whether an app contains known malware, and whether the developer’s signing certificate is revoked.

Apple's OCSP service uses HTTPS encryption, so only they are able to see which apps you open. They've posted information about their logging policy for this service. They additionally promised to add a mechanism for people to opt-out of this online check, but this has not been added to macOS.

While you can manually opt out of this check relatively easily, we recommend against doing so unless you would be badly compromised by the revocation checks performed by macOS, because they serve an important role in ensuring compromised apps are blocked from running.

Your account when you first set up your Mac will be an Administrator account, which has higher privileges than a Standard user account. macOS has a number of protections which prevent malware and other programs from abusing your Administrator privileges, so it is generally safe to use this account.

However, exploits in protective utilities like sudo have been discovered in the past. If you want to avoid the possibility that programs you run abuse your Administrator privileges, you could consider creating a second, Standard user account which you use for day-to-day operations. This has the added benefit of making it more obvious when an app needs admin access, because it will prompt you for credentials every time.

If you do use a second account, it is not strictly required to ever log in to your original Administrator account from the macOS login screen. When you are doing something as a Standard user which requires Administrator permissions, the system should prompt you for authentication, where you can enter your Administrator credentials as your Standard user on a one-time basis. Apple provides guidance on hiding your Administrator account if you prefer to only see a single account on your login screen.

iCloud

When you use Apple services like iCloud, most of your information is stored on their servers and secured with keys which Apple has access to by default. This is called Standard Data Protection by Apple.

Therefore, if you use iCloud you should enable Advanced Data Protection. This encrypts nearly all of your iCloud data with keys stored on your devices (end-to-end encryption), rather than Apple's servers, so that your iCloud data is secured in the event of a data breach, and otherwise hidden from Apple.

If you want to be able to install apps from the App Store but don't want to enable iCloud, you can sign in to your Apple Account from the App Store instead of System Settings.

System Settings

There are a number of built-in settings you should confirm or change to harden your system. Open the Settings app:

Bluetooth

  • Uncheck Bluetooth (unless you are currently using it)

Network

Depending on if you are using Wi-Fi or Ethernet (denoted by a green dot and the word "connected"), click on the corresponding icon.

Click on the "Details" button by your network name:

  • Select Rotating under Private Wi-Fi address

  • Check Limit IP address tracking

Firewall

Your firewall blocks unwanted network connections. The stricter your firewall settings are, the more secure your Mac is. However, certain services will be blocked. You should configure your firewall to be as strict as you can without blocking services you use.

  • Check Firewall

Click the Options button:

  • Check Block all incoming connections

If this configuration is too strict, you can come back and uncheck this. However, macOS will typically prompt you to allow incoming connections for an app if the app requests it.

General

By default, your device name will be something like "[your name]'s iMac". Because this name is publicly broadcast on your network, you'll want to change your device name to something generic like "Mac".

Click on About and type your desired device name into the Name field.

Software Updates

You should automatically install all available updates to make sure your Mac has the latest security fixes.

Click the small icon next to Automatic Updates:

  • Check Check for updates

  • Check Download new updates when available

  • Check Install macOS updates

  • Check Install application updates from the App Store

  • Check Install Security Responses and system files

Privacy & Security

Whenever an application requests a permission, it will show up here. You can decide which applications you want to allow or deny specific permissions.

Location Services

You can individually allow location services per-app. If you don't need apps to use your location, turning off location services entirely is the most private option.

  • Uncheck Location Services
Analytics & Improvements

Decide whether you want to share analytics data with Apple and developers.

  • Uncheck Share Mac Analytics

  • Uncheck Improve Siri & Dictation

  • Uncheck Share with app developers

  • Uncheck Share iCloud Analytics (visible if you are signed in to iCloud)

Apple Advertising

Decide whether you want personalized ads based on your usage.

  • Uncheck Personalized Ads
FileVault

On modern devices with a Secure Enclave (Apple T2 Security Chip, Apple silicon), your data is always encrypted, but is decrypted automatically by a hardware key if your device doesn't detect it's been tampered with. Enabling FileVault additionally requires your password to decrypt your data, greatly improving security, especially when powered off or before the first login after powering on.

On older Intel-based Mac computers, FileVault is the only form of disk encryption available by default, and should always be enabled.

  • Click Turn On
Lockdown Mode

Lockdown Mode disables some features in order to improve security. Some apps or features won't work the same way they do when it's off, for example, JIT and WASM are disabled in Safari with Lockdown Mode enabled. We recommend enabling Lockdown Mode and seeing whether it significantly impacts your usage, many of the changes it makes are easy to live with.

  • Click Turn On

MAC Address Randomization

macOS uses a randomized MAC address when performing Wi-Fi scans while disconnected from a network.

You can set your MAC address to be randomized per network and rotate occasionally to prevent tracking between networks and on the same network over time.

Go to System Settings → Network → Wi-Fi → Details and set Private Wi-Fi address to either Fixed if you want a fixed but unique address for the network you're connected to, or Rotating if you want it to change over time.

Consider changing your hostname as well, which is another device identifier that's broadcast on the network you're connected to. You may wish to set your hostname to something generic like "MacBook Air", "Laptop", "John's MacBook Pro", or "iPhone" in System Settings → General → Sharing. Some privacy scripts allow you to easily generate hostnames with random names.

Security Protections

macOS employs defense in depth by relying on multiple layers of software and hardware-based protections, with different properties. This ensures that a failure in one layer does not compromise the system's overall security.

Software Security

Warning

macOS allows you to install beta updates. These are unstable and may come with extra telemetry since they're for testing purposes. Because of this, we recommend you avoid beta software in general.

Signed System Volume

macOS's system components are protected in a read-only signed system volume, meaning that neither you nor malware can alter important system files.

The system volume is verified while it's running and any data that's not signed with a valid cryptographic signature from Apple will be rejected.

System Integrity Protection

macOS sets certain security restrictions that can't be overridden. These are called Mandatory Access Controls, and they form the basis of the sandbox, parental controls, and System Integrity Protection on macOS.

System Integrity Protection makes critical file locations read-only to protect against modification from malicious code. This is on top of the hardware-based Kernel Integrity Protection that keeps the kernel from being modified in-memory.

Application Security

App Sandbox

On macOS, whether an app is sandboxed is determined by the developer when they sign it. The App Sandbox protects against vulnerabilities in the apps you run by limiting what a malicious actor can access in the event that the app is exploited. The App Sandbox alone can't protect against Supply Chain Attacks by malicious developers. For that, sandboxing needs to be enforced by someone other than the developer themselves, as it is on the App Store.

Warning

Software downloaded from outside the official App Store is not required to be sandboxed. If your threat model prioritizes defending against Passive Attacks, then you may want to check if the software you download outside the App Store is sandboxed, which is up to the developer to opt in.

You can check if an app uses the App Sandbox in a few ways:

You can check if apps that are already running are sandboxed using the Activity Monitor.

Warning

Just because one of an app's processes is sandboxed doesn't mean they all are.

Alternatively, you can check apps before you run them by running this command in the terminal:

% codesign -dvvv --entitlements - <path to your app>

If an app is sandboxed, you should see the following output:

    [Key] com.apple.security.app-sandbox
    [Value]
        [Bool] true

If you find that the app you want to run is not sandboxed, then you may employ methods of compartmentalization such as virtual machines or separate devices, use a similar app that is sandboxed, or choose to not use the unsandboxed app altogether.

Hardened Runtime

The Hardened Runtime is an extra form of protection for apps that prevents certain classes of exploits. It improves the security of apps against exploitation by disabling certain features like JIT.

You can check if an app uses the Hardened Runtime using this command:

codesign --display --verbose /path/to/bundle.app

If Hardened Runtime is enabled, you will see flags=0x10000(runtime). The runtime output means Hardened Runtime is enabled. There might be other flags, but the runtime flag is what we're looking for here.

You can enable a column in Activity Monitor called "Restricted" which is a flag that prevents programs from injecting code via macOS's dynamic linker. Ideally, this should say "Yes".

Antivirus

macOS comes with two forms of malware defense:

  1. Protection against launching malware in the first place is provided by the App Store's review process for App Store applications, or Notarization (part of Gatekeeper), a process where third-party apps are scanned for known malware by Apple before they are allowed to run. Apps are required to be signed by the developers using a key given to them by Apple. This ensures that you are running software from the real developers. Notarization also requires that developers enable the Hardened Runtime for their apps, which limits methods of exploitation.
  2. Protection against other malware and remediation from existing malware on your system is provided by XProtect, a more traditional antivirus software built-in to macOS.

We recommend against installing third-party antivirus software as they typically do not have the system-level access required to properly function anyways, because of Apple's limitations on third-party apps, and because granting the high levels of access they do ask for often poses an even greater security and privacy risk to your computer.

Backups

macOS comes with automatic backup software called Time Machine, so you can create encrypted backups to an external drive or a network drive in the event of corrupted/deleted files.

Hardware Security

Many modern security features in macOS—such as modern Secure Boot, hardware-level exploit mitigation, OS integrity checks, and file-based encryption—rely on Apple silicon, and Apple's newer hardware always has the best security. We only encourage the use of Apple silicon, and not older Intel-based Mac computers or Hackintoshes.

Some of these modern security features are available on older Intel-based Mac computers with the Apple T2 Security Chip, but that chip is susceptible to the checkm8 exploit which could compromise its security.

If you use Bluetooth accessories such as a keyboard, we recommend that you use official Apple ones as their firmware will automatically be updated for you by macOS. Using third party accessories is fine, but you should remember to install firmware updates for them regularly.

Apple's SoCs focus on minimizing attack surface by relegating security functions to dedicated hardware with limited functionality.

Boot ROM

macOS prevents malware persistence by only allowing official Apple software to run at boot time; this is known as secure boot. Mac computers verify this with a bit of read-only memory on the SoC called the boot ROM, which is laid down during the manufacturing of the chip.

The boot ROM forms the hardware root of trust. This ensures that malware cannot tamper with the boot process. When your Mac boots up, the boot ROM is the first thing that runs, forming the first link in the chain of trust.

Mac computers can be configured to boot in three security modes: Full Security, Reduced Security, and Permissive Security, with the default setting being Full Security. You should ideally be using Full Security mode and avoid things like kernel extensions that force you to lower your security mode. Make sure to check that you're using Full Security mode.

Secure Enclave

The Secure Enclave is a security chip built into devices with Apple silicon which is responsible for storing and generating encryption keys for data at rest as well as Face ID and Touch ID data. It contains its own separate boot ROM.

You can think of the Secure Enclave as your device's security hub: it has an AES encryption engine and a mechanism to securely store your encryption keys, and it's separated from the rest of the system, so even if the main processor is compromised, it should still be safe.

Touch ID

Apple's Touch ID feature allows you to securely unlock your devices using biometrics.

Your biometric data never leaves your device; it's stored only in the Secure Enclave.

Hardware Microphone Disconnect

All laptops with Apple silicon or the T2 chip feature a hardware disconnect for the built-in microphone whenever the lid is closed. This means that there is no way for an attacker to listen to your Mac's microphone even if the operating system is compromised.

Note that the camera does not have a hardware disconnect, since its view is obscured when the lid is closed anyway.

Peripheral Processor Security

Computers have built-in processors other than the main CPU that handle things like networking, graphics, power management, etc. These processors can have insufficient security and become compromised, therefore Apple tries to minimize the need for these processors in their hardware.

When it is necessary to use one of these processors, Apple works with the vendor to ensure that the processor

  • runs verified firmware from the primary CPU on startup
  • has its own Secure Boot chain
  • follows minimum cryptographic standards
  • ensures known bad firmware is properly revoked
  • has its debug interfaces disabled
  • is signed with Apple's cryptographic keys

Direct Memory Access Protections

Apple silicon separates each component that requires direct memory access. For example, a Thunderbolt port can't access memory designated for the kernel.

Sources

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