System Hardening Checklist

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About this System Hardening Checklist Page
Contributor maintained wiki page.
Support Status stable
Difficulty easy
Contributor torjunkiearchive.org
Support Support

Kicksecure comes with many security featuresarchive.org. Kicksecure is hardened by default and also provides extensive Documentation including this System Hardening Checklist. The more you know, the safer you can be.

This page is targeted at users who wish to improve the security of their systems for even greater protection.

Introduction[edit]

Info Recommendations specific to Kicksecure-Qubes or Kicksecure are marked accordingly.

It is possible to significantly harden the Kicksecure and/or host platform. This reduces the likelihood of a temporary or persistent compromise, while increasing the chances of successful, secure activity. Hardening is dependent upon a user's skill set, motivation and available hardware. The checklist below is intended to provide a quick overview of important issues, categorized by difficulty level - easy, moderate, difficult and expert.

Easy[edit]

Command Line Operations[edit]

  • Do not run commands unless they are completely understood -- first refer to a suitable Kicksecure wiki resource if available.
  • If root privileges are required, run the command with sudo rather than logging in as root or using sudo su. [1]
  • Defeat login spoofing by using the Secure Access Key ("Sak"; SysRq + k) procedure.
  • Consider enabling SysRq "Security Keys" functionality as insurance against system malfunctions -- this assists in system recovery efforts and limits the potential harm of a malware compromise.

Disabling and Minimizing Hardware Risks[edit]

Entropy[edit]

  • To mitigate against inadequate entropy seeding by the Linux Random Number Generator (RNG), it is recommended to install daemons that inject more randomness into the pool.

File Handling[edit]

Info Kicksecure-Qubes only.

  • In File Manager, disable previews of files from untrusted sources. Change file preferences in the Template's File Manager so future App Qubes inherit this feature.
  • Files received or downloaded from untrusted sources (the internet, via email etc.) should not be opened in a trusted VM. Instead, open them in a Disposables: Right-clickOpen In Disposables
  • Untrusted PDFs should be opened in a Disposables or converted into a trusted (sanitized) PDFarchive.org to prevent exploitation of the PDF reader and potential infection of the VM.

File Folder Permissions[edit]

  • Linux user account nobody has no special meaning.
  • Also linux user group nogroup has no special meaning either.
  • Therefore the user should avoid running programs under user nobody and/or group nogroup as well as avoid setting file or folder permissions to that user / group.

[10]

File Storage Location[edit]

Mandatory Access Control[edit]

Mobile Devices[edit]

Phones, smartphones, smartwatches, tablets and similar mobile devices are vulnerable to advanced malware and can be abused for eavesdropping, espionage, location tracing and more. Since the mobile devices security best practices for risk mitigation are often difficult / infeasible to adhere, it might be easier to physically move all mobiles devices to a distant physical location such as a different room and close the door and/or to power off mobile devices.

Passwords and Logins[edit]

  • Use strong, unique and random passwords for all online accounts, system logins and encryption / decryption purposes to prevent the feasibility of brute-forcing attacks.
  • Use a trusted password manager (KeePassXC) [12], so hundreds of different passwords can be kept stored in an encrypted password database, protected by one strong master password. [13]
  • For high-entropy passwords, consider using Diceware passphrases. [14]
  • In Kicksecure-Qubes, store all login credentials and passwords in an offline vault VM (preferably with KeePassXC) and securely cut and paste them into the browser. [15]
  • Read and follow all the principles for stronger passwords.

Screensavers[edit]

Secure Downloads[edit]

  • Download Internet files securely using scurl instead of wget from the command line.
  • When downloading with a browser, prevent SSLstrip attacks by typing https:// links directly into the URL / address bar.

Secure Qubes Operation[edit]

Info Kicksecure-Qubes only.

Secure Software Installation[edit]

Updates[edit]

  • Operating System Updates: It is crucial to regularly check for operating system updates on the host operating system Kicksecure (or in a VM).
  • Stay tuned: It is absolutely crucial to subscribe to and read the latest Kicksecure news category 'important-news' to stay in touch with ongoing developments. This way users benefit from notifications concerning important security advisories, potential upgrade issues and improved releases which address identified issues, like those affecting the updater or other core elements. Follow Kicksecure Developments.
  • Debian Security Announcements: Since Kicksecure is based on Debian, users should consider subscribing to the Debian security announcement mailing listarchive.org to stay informed about the latest security advisories. See also chapter Debian Security Announcements.

Virtual Machines[edit]

All Virtualizers[edit]

VirtualBox[edit]

Warrant Canary[edit]

Moderate[edit]

Create a USB Qube[edit]

Info Kicksecure-Qubes only.

Kicksecure as a Host Operating System Hardening[edit]

All Platforms[edit]

Kernels / Kernel Modules[edit]

Info Note:

  • Cutting-edge kernels can destabilize the system or cause boot failures.
  • Newer kernels can expose additional vulnerabilities; see footnotes. [24] [25]
  • Kernel modules in Qubes and Kicksecure-Qubes usually require configuration of a Qubes VM Kernel.

Live-mode[edit]

Info Kicksecure only.

Networking[edit]

All Platforms[edit]

  • If possible, use a dedicated network connection (LAN, WiFi etc.) that is not shared with other potentially compromised computers.
  • If using a shared network via a common cable modem/router or ADSL router, configure a de-militarized zone (perimeter network). [33]
  • Test the LAN's router/firewall with either an internet port scanning service or preferably a port scanning application from an external IP address.
  • Change the default administration password on the router to a unique, random, and suitably long Diceware passphrase to prevent bruteforcing attacks.
  • WiFi users should default to the WPA2-AESarchive.org (avoid TKIParchive.org) or WPA3archive.org standard; the protocols are safer and have stronger encryption. [34] [35]
  • Follow all other Kicksecure recommendations to lock down the router.
  • Disable TCP Selective Acknowledgement (SACK)archive.org unless it is required, since it is a commonly exploited option in the TCP protocol and not needed for many people; see footnotes. [36] [37] [38]

Kicksecure-Qubes Only[edit]

  • Prefer the Kicksecure Template for networking (sys-net and sys-firewall) since it is minimal in naturearchive.org and does not "ping home", unlike the Fedora Template. [39]
  • Consider using customized minimal templatesarchive.org for NetVMs to reduce the attack surface and memory requirements.

Sandboxing[edit]

Spoof MAC Addresses[edit]

Info Tip: MAC spoofingarchive.org is only necessary if traveling with your laptop or PC. It is not required for home PCs that do not change locations.

Time Related[edit]

Tor Settings[edit]

Info Tor is used in Kicksecure for updates, time fixes and other operations.

Kicksecure VM Security[edit]

Difficult[edit]

Anti-Evil Maid[edit]

  • Consider the Android Haven applicationarchive.org for sensitive devices -- motion, sound, vibration and light sensors can monitor and protect physical areas. [45]
  • If a Trusted Platform Module (TPM) is available, enable it in BIOS/UEFI and configure the required servicesarchive.org to protect against Evil Maid Attacks.
    • Kicksecure-Qubes: Utilize AEM protectionarchive.org to attest that only desired (trusted) components are loaded and executed during the system boot. [46]

Disposabless[edit]

Info Qubes / Kicksecure-Qubes only.
Note: Some traces of Disposables usage and data contents will leak into the dom0 filesystem and survive reboots; see herearchive.org for further information. (This is a Qubes-specific issue and unrelated to Kicksecure.)

  • Run all instances of Firefox in a Disposablesarchive.org (.oniononion) which is preferably uncustomized to resist fingerprinting.
  • Configure each ServiceVM as a static Disposablesarchive.org to mitigate the threat from persistent malware accross VM reboots. [47]

Email[edit]

All Platforms[edit]

Kicksecure-Qubes Only[edit]

  • Use split-GPGarchive.org for email to reduce the risk of key theft used for encryption / decryption and signing.
  • Create an App Qube that is exclusively used for email and change the VM's firewall settings to only allow network connections to the email server and nothing else ("Deny network access except...").
  • Only open untrusted email attachmentsarchive.org in a Disposables to prevent possible infection.

Ethernet/FDDI Station Activity Monitor[edit]

Flash the Router with Opensource Firmware[edit]

Warning: risk of bricking your router!

Multi-Factor User Authentication[edit]

  • Set up two-factor authentication (2FA) to strengthen the security of online accounts, smartphones, web services, access to physical locations and other implementations.
  • Configure PAM USBarchive.org as a module that only allows user authentication by inserting a token (a USB stick), in which a one-time password is stored.
  • For secure account logins, utilize a Nitrokeyarchive.org hardware authentication device which supports one-time passwords, public-key encryption, and the Universal 2nd Factor (U2F) and FIDO2 protcols.
    • Qubes: Follow the YubiKeyarchive.org instructions (you can adjust it to be compatible with nitrokey) to enhance the security of Qubes user authentication, mitigate the risk of password snooping, and to improve USB keyboard security.

Systemd Sandboxing[edit]

Expert[edit]

Disable Intel ME Functionality[edit]

Warning: high risk of bricking your computer!

Disable SUID-enabled Binaries[edit]

Info This is an experimental feature recommended for testers.

Opensource Firmware[edit]

  • Librebootarchive.org is no longer recommended as a proprietary firmware alternative; see footnote. [52]
  • Corebootarchive.org is a possible BIOS/UEFI firmware alternative -- consider purchasing hardware that has it pre-installed (like Chromebooks), or research flashing procedures for the handful of refurbished motherboards that support it.

Footnotes[edit]

  1. This reduces the likelihood of a successful root or non-root user compromise.
  2. Kicksecure 16 and later versions disable the root account by default.
  3. https://forums.whonix.org/t/use-sudoedit-in-whonix-documentation/7599archive.org
  4. This addresses spying techniques:
  5. This applies to both Intel and AMD architecture.
  6. While this may introduce new vulnerabilities, this is objectively better than running a system that is vulnerable to known attacks.
  7. This hides hardware identifiers from unprivileged users.
  8. sudo apt install jitterentropy-rngd
  9. sudo apt install haveged
  10. https://forums.whonix.org/t/delete-disable-nobody-user-from-whonix-passwd/14085archive.org
  11. The reason is AppArmor profiles (and possibly other mandatory access control frameworks) are unlikely to allow access to these folders by default.
  12. Debian KeePassXC packagearchive.org.
  13. For greater security, store the password manager off-line.
  14. To estimate strength, an 8-word Diceware passphrase provides ~90 bits of entropy, while a 10-word passphrase provides ~128 bits of entropy.
  15. For greater safety, copy something else into the clipboard after pasting so the password is purged and cannot be accidentally pasted elsewhere.
  16. For example, sensitive notificationsarchive.org (pop up dialog boxes) can appear over the screensaver while lockedarchive.org, and screensaver bypassarchive.org bugsarchive.org are common. Screen Locker (In)Security - Can we disable these at least 4 backdoors?archive.org
  17. Also see: Disconnecting a video output can cause XScreenSaver to crash (QSB-068, CVE-2021-34557)archive.org.
  18. The Kicksecure and Debian repositories are no longer set to onion mirrors by default due to stability issues. This decision will be reviewed in the future once v3 onions have further matured.
  19. If a keyserver is required, utilize the v3 onion address for keys.openpgp.org: http://zkaan2xfbuxia2wpf7ofnkbz6r5zdbbvxbunvp5g2iebopbfc4iqmbad.oniononion
  20. Bidirectional clipboard sharing is currently enabled by default in Kicksecure VirtualBox VMs. There are security reasons to disable clipboard sharing, for example to prevent the accidental copying of something (non-)anonymous and pasting it in its (non-)anonymous counterpart such as a browser, which would lead to identity correlation.
  21. Providing a mechanism to access files of the host system from within the guest system via a specially defined path necessarily enlarges the attack surface and provides a potential pathway for malicious actors to compromise the host.
  22. A USB qube is automatically created as of Qubes R4.0.
  23. USB keyboards and mice expose dom0 to attacks, and all USB devices are potential side channel attack vectorsarchive.org.
  24. The Truth about Linux 4.6archive.org:

    The real "hard truth" about Linux kernel security is that there's no such thing as a free lunch. Keeping up to date on the latest upstream kernel will generally net all the bug fixes that have been created thus far, but with it of course brings completely new features, new code, new bugs, and new attack surface. The majority of vulnerabilities in the Linux kernel are ones that have been released just recently, something any honest person active in kernel development can attest to.

  25. Kicksecure contributor madaidan has notedarchive.org:

    LTS kernels have less hardening features and not all bug fixes are backported but it has less attack surface and potentially less chance of having bugs. Stable kernels have more hardening features and all bug fixes but more attack surface and more bugs.

  26. Including grsecurity elementsarchive.org being mainlined by the Kernel Self Protection Projectarchive.org.
  27. This will likely become the default in future, see: Simplify and promote using in-vm kernelarchive.org.
  28. Do not raise Qubes VM Kernel issues at Kicksecure. Instead, contact Qubes supportarchive.org.
  29. https://forums.whonix.org/t/what-to-post-in-this-qubes-whonix-forum-and-what-not/2275archive.org
  30. The TCP Initial Sequence Numbers (ISNs) are randomized.
  31. tirdadarchive.org is installed in Kicksecure by default.
  32. This prevents remounting of the hard drive as read-write.
  33. This restricts Kicksecure accessibility to/from other nodes on the network such as printers, phones and laptops.
  34. WPA3 protocol improvementsarchive.org include:
    • Protection against brute force “dictionary” attacks -- adversaries cannot make multiple login attempts with commonly used passwords.
    • Stronger encryption: WPA2 relies on a 64-bit or 128-bit encryption key, but WPA3 uses 192-bit encryption.
    • Use of individualized data encryption in open networks to strengthen user privacy.
    • Forward secrecyarchive.org: if an adversary captures encrypted Wi-Fi transmissions and cracks the password, they cannot use it to read older data.
  35. Do not rely on WiFi Protected Set-up (WPS), which has major security flawsarchive.org.
  36. For example, it has been used for remote denial of service attacksarchive.org and can even lead to a Linux kernel panic.
  37. 1. Open file /etc/sysctl.d/30_security-misc.conf in an editor with root rights.

    Kicksecure

    This box uses sudoedit for better security.

    Kicksecure for Qubes

    NOTE: When using Kicksecure-Qubes, this needs to be done inside the Template.

    Others and Alternatives

    • This is just an example. Other tools could achieve the same goal.
    • If this example does not work for you or if you are not using Kicksecure, please refer to this link.

    sudoedit /etc/sysctl.d/30_security-misc.conf

    2. Uncomment all lines starting with net.ipv4.

    Note: This procedure can also be repeated in Kicksecure.

    TCP SACK is not disabled by default because on some systems it can greatly decrease network performance.

  38. https://forums.whonix.org/t/disabling-tcp-sack-dsack-fack/8109/5archive.org
  39. https://forums.whonix.org/t/disable-sys-net-pings-to-fedoraproject-org/1952archive.org
  40. Although not implemented yet, all user-installed applications will be automatically configured to run in the sandbox and a prompt will ask which permissions should be granted to the application.
  41. Such as system information, host time, system uptime, and fingerprinting of devices behind a router.
  42. This prevents time-related attack vectors which rely on leakage of the host time.
  43. https://forums.whonix.org/t/tor-connectionpadding/7477archive.org
  44. For example, Kicksecure users residing in China.
  45. Notifications are made in real time for any potentially suspicious activity.
  46. Unauthorized modifications to BIOS or the boot partition will be notified.
  47. Users can configure sys-net, sys-firewall and sys-usb as static Disposabless. This option has been available from Qubes R4 onward.
  48. Reminder: The Subject: line and other header fields are not encrypted in the current configuration.
  49. Attackers use these methods to redirect local network traffic and execute Man-in-the-middle Attacks.
  50. Administrators are advised of any changes via email, such as new station/activity, flip-flops and re-used/changed old addresses.
  51. This reduces the attack surface by disabling SUID-enabled binaries and improves Strong Linux User Account Isolation. Some SUID binaries have a history of privilege escalation security vulnerabilities. This feature is part of security-misc.
  52. Although Libreboot is a free, opensource BIOS or UEFI replacement that initializes the hardware and starts the bootloader for the OS, the absence of proprietary firmware means important microcode security updates are unavailable. Also, even experts risk bricking their hardware during the process and it is incompatible with newer architectures, making it impractical for the majority of the Kicksecure population.

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