{{Header}} {{Title|
title=System Hardening Checklist
}} {{#seo:
|description=Security hardening instructions for {{project_name_long}} and {{q_project_name_long}}. Improving Linux, Windows and macOS host computer security and networking configurations. Safe Tor, Tor Browser and other online activities.
|image=Hardening-13423213.jpg
}} {{Contributor|
|status=stable
|about=About this {{PAGENAME}} Page
|difficulty=easy
|contributor=[https://forums.whonix.org/users/torjunkie torjunkie]
|support=[[Support]]
}} [[File:Kicksecure-image-seal.svg|thumb|200px]] [[File:Hardening-13423213.jpg|thumb]]
{{intro|
{{project_name_short}} comes with [https://www.{{project_clearnet}}/#security many security features]. {{project_name_short}} 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 =

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| text    = Recommendations specific to [[Qubes|{{q_project_name_short}}]] or [[{{non_q_project_name_short}}|{{non_q_project_name_short}}]] are marked accordingly.
}}

It is possible to significantly harden the {{project_name_short}} 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 =

== Command Line Operations ==

* Do not run commands unless they are completely understood -- first refer to a suitable [[Documentation|{{project_name_short}} wiki resource]] if available.
* If [[Root|root privileges]] are required, run the command with <code>sudo</code> rather than logging in as root or using <code>sudo su</code>. <ref>This reduces the likelihood of a successful root or non-root user compromise.</ref>
** Consider [[Root#Disable_Root_Account|disabling the root account]] permanently. <ref>{{project_name_short}} 16 and later versions disable the root account by default.</ref>
** To prevent malware sniffing the root password, before performing administrative tasks that require root access, [[Root#Prevent_Malware_from_Sniffing_the_Root_Password|create an <code>admin</code> user account with sudo permissions]].
** Prefer <code>sudoedit</code> for better security when editing files. <ref>
https://forums.whonix.org/t/use-sudoedit-in-whonix-documentation/7599
</ref>
* [[Login spoofing|Defeat login spoofing]] by using the Secure Access Key ("Sak"; <code>SysRq</code> + <code>k</code>) 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 ==

* Unplug external devices when not needed.
* Consider [[Hardware_Threat_Minimization#Microphones|disabling microphones]] where possible (muting on the host) or better, physically removing them.
* Since speakers (all audio output devices) can be turned into microphones, if possible, [[Hardware_Threat_Minimization#Speakers|physically remove speakers on the host and remove/disable the beeper]]. <ref>
This addresses spying techniques:

* [https://arxiv.org/ftp/arxiv/papers/1611/1611.07350.pdf SPEAKE(a)R: Turn Speakers to Microphones for Fun and Profit]
* relying on watermarked, (in)audible sounds that can link multiple devices, as well as [https://arxiv.org/ftp/arxiv/papers/1611/1611.07350.pdf headphones/speakers being covertly used as a microphone].
</ref>
* Preferably [[Hardware_Threat_Minimization#Webcams|detach webcams or even better, physically cover webcams with a sticker or switch]] unless they are in use.
** If using [[Qubes|{{q_project_name_short}}]], assign the webcam to an untrusted VM (if needed).
* Avoid using [[Hardware_Threat_Minimization#Wireless_Input_Devices|wireless devices]], since they are insecure.
* Preferably disable or remove [https://en.wikipedia.org/wiki/Bluetooth#History_of_security_concerns Bluetooth hardware modules].
* Disable or remove [[Protection_Against_Physical_Attacks#Problematic_Interfaces|problematic devices]] like ExpressCard, PCMCIA, FireWire or Thunderbolt which may allow attackers with physical access to read RAM.
* Do not enable audio input to any VM unless strictly required.
* Apply [[Firmware_Security_and_Updates#Firmware_Updating_and_Security_Problems|CPU microcode updates]] <ref>
This applies to both Intel and AMD architecture.
</ref>. <ref>
While this may introduce new vulnerabilities, this is objectively better than running a system that is vulnerable to known attacks.
</ref>
* Consider [[Security-misc#Restrict_Hardware_Information_to_Root|restricting hardware information to the root user]] in {{project_name_short}}. <ref>
This hides hardware identifiers from unprivileged users.
</ref>
* In [[Qubes|{{q_project_name_short}}]], only use a mouse and keyboard utilizing PS/2 ports (not USB ports) to prevent [https://theinvisiblethings.blogspot.fr/2011/06/usb-security-challenges.html malicious compromise] of dom0 (PS/2 adapters and available controllers are required).

== Entropy ==

* 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.
** From [https://www.debian.org/releases/stable/ Debian Stable], [[Dev/Entropy#jitterentropy|jitterentropy-rngd]] is available; see footnote. <ref>{{CodeSelect|code=
sudo apt install jitterentropy-rngd
}}
</ref>
** [[Dev/Entropy#haveged|haveged]] also uses CPU timer jitter to generate entropy and additional entropy sources cannot hurt; see footnote. <ref>{{CodeSelect|code=
sudo apt install haveged
}}
</ref>

== File Handling ==

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* 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: <code>Right-click</code> &rarr; <code>Open In Disposables</code>
* Untrusted PDFs should be opened in a Disposables or converted into a [https://github.com/QubesOS/qubes-app-linux-pdf-converter trusted (sanitized) PDF] to prevent exploitation of the PDF reader and potential infection of the VM.

== File Folder Permissions ==

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

<ref>
https://forums.whonix.org/t/delete-disable-nobody-user-from-whonix-passwd/14085
</ref>

== File Storage Location ==

* Avoid storing files directly in the root home folder and [[Computer_Security_Introduction#File_Storage_Location|create appropriate sub-folders instead]].
* Move files downloaded by Firefox from the <code>~/Downloads</code> folder to another specially created one. <ref>The reason is AppArmor profiles (and possibly other mandatory access control frameworks) are unlikely to allow access to these folders by default.</ref>

== Mandatory Access Control ==

* Enable all available [[AppArmor|apparmor profiles]] in the {{project_name_short}} Templates.
* Enable [[Seccomp|seccomp]] on {{project_name_gateway_long}}.

== Mobile Devices ==
{{mbox
| image   = [[File:Ambox_warning_pn.svg.png|40px]]
| text    = '''Warning:''' Phones, smartphones, smartwatches, tablets and similar mobile devices are {{kicksecure_wiki
|wikipage=Mobile_Phone_Security#Advanced_Mobile_Phone_Spyware
|text=vulnerable to advanced malware
}} and can be abused for eavesdropping, espionage, location tracing and more.
}}

* Since the {{kicksecure_wiki
|wikipage=Mobile_Phone_Security#Best_Practices
|text=mobile devices security best practices for risk mitigation
}} are often difficult / infeasible to adhere to, 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 ==

* Use strong, unique and random [[Passwords|passwords]] for all online accounts, system logins and encryption / decryption purposes to prevent the feasibility of brute-forcing attacks.
* Use a trusted [[Keepassxc|password manager (KeePassXC)]] <ref>
[https://packages.debian.org/{{stable project version based on Debian codename}}/keepassxc Debian KeePassXC package].
</ref>, so hundreds of different passwords can be kept stored in an encrypted password database, protected by one strong master password. <ref>
For greater security, store the password manager off-line.
</ref>
* For high-entropy passwords, consider using [[Passwords#Generating_Unbreakable_Passwords|Diceware passphrases]]. <ref>
To [[Passwords#Diceware_Password_Strength|estimate strength]], an 8-word Diceware passphrase provides ~90 bits of entropy, while a 10-word passphrase provides ~128 bits of entropy.
</ref>
* In [[Qubes|{{q_project_name_short}}]], store all login credentials and passwords in an offline vault VM (preferably with KeePassXC) and securely cut and paste them into the browser. <ref>
For greater safety, copy something else into the clipboard after pasting so the password is purged and cannot be accidentally pasted elsewhere.
</ref>
* Read and follow all the [[Passwords#Principles_for_Stronger_Passwords|principles for stronger passwords]].

== Screensavers ==
* At a minimum, [[Protection_Against_Physical_Attacks#Screen_Lock|lock the screen of the host]] when it is unattended.
* For better security, shut down the computer entirely -- screensavers are notoriously insecure. <ref>
For example, [https://www.jwz.org/xscreensaver/faq.html#popup-windows sensitive notifications] (pop up dialog boxes) can [https://github.com/QubesOS/qubes-issues/issues/2026 appear over the screensaver while locked], and screensaver [https://www.debian.org/security/2016/dsa-3438 bypass] [https://web.archive.org/web/20210925121730/https://bugs.archlinux.org/index.php?do=details&task_id=27993 bugs] are common.

[https://forums.whonix.org/t/screen-locker-in-security-can-we-disable-these-at-least-4-backdoors/8128 Screen Locker (In)Security - Can we disable these at least 4 backdoors?]
</ref> <ref>Also see: [https://github.com/QubesOS/qubes-issues/issues/6595 Disconnecting a video output can cause XScreenSaver to crash (QSB-068, CVE-2021-34557)].</ref>

== Secure Downloads ==

* Download Internet files [[Secure_Downloads|securely]] using <i>scurl</i> instead of <i>wget</i> from the command line.
* When downloading with a browser, prevent SSLstrip attacks by typing <code>https://</code> links directly into the URL / address bar.

== Secure Qubes Operation ==

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* Refer to the [[{{q_project_name_short}}_Security|{{q_project_name_short}} security recommendations]] and always follow the [https://www.qubes-os.org/news/ latest security news] and [https://github.com/Qubes-Community/Contents/blob/master/docs/security/security-guidelines.md advice] from the Qubes team.

== Secure Software Installation ==

* <s>Default to Debian's {{kicksecure_wiki
|wikipage=Install_Software#Best_Practices
|text=official package manager APT
}} for installing software, and avoid third party package managers.</s> See {{kicksecure_wiki
|wikipage=Install_Software
|text=Install Software
}}.
* When possible, use mechanisms which simplify and automate software upgrades and installations, like <i>apt</i> functions.
* Prefer installation of software from [[Install_Software#Best_Practices|signed (Debian) GNU/Linux repositories]] and avoid manually installing software, particularly if it is unsigned.
* Set the Qubes, Debian and {{project_name_short}} package updates to [[Onionizing_Repositories|Tor onion service repositories]]. <ref>The {{project_name_short}} 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.</ref>
* For safer installations or updates, first [[Install_Software#How-to:_Install_or_Update_with_Utmost_Caution|stop all activity/applications and rotate the Tor circuits]].
* Always [[Verifying_Software_Signatures|verify key fingerprints and digital signatures of signed software]] before importing keys or installing software.
** Avoid using [[OpenPGP#Key_Servers|keyservers]] if possible.
** It is safer to [[Secure Downloads|securely download]] the key from a source that is logically connected to the owner, if possible, outside the keyserver model. <ref>If a keyserver is required, utilize the v3 onion address for <code>keys.openpgp.org</code>:  <code>http://zkaan2xfbuxia2wpf7ofnkbz6r5zdbbvxbunvp5g2iebopbfc4iqmbad.onion</code></ref>

== Updates ==
* <u>Operating System Updates</u>: It is crucial to regularly check for [[Operating_System_Software_and_Updates#Updates|operating system updates]] on the host operating system {{project_name_short}} (or in a VM).
* <u>Stay tuned</u>: It is [[Stay_Tuned#Reason|absolutely crucial]] to subscribe to and read the latest {{project_name_short}} 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. [[Stay_Tuned|Follow {{project_name_short}} Developments]].
* <u>Debian Security Announcements</u>: Since {{project_name_short}} is [[About#Based_on_Debian|based on Debian]], users should consider subscribing to the Debian [https://lists.debian.org/debian-security-announce/ security announcement mailing list] to stay informed about the latest security advisories. See also chapter [[Operating_System_Hardening#Debian_Security_Announcements|Debian Security Announcements]].

== Virtual Machines ==
=== All Virtualizers ===
* Remove the virtual audio controller to VMs from getting access to a [[Hardware_Threat_Minimization#Microphone|microphone (eavesdropping risk)]] or [[Hardware_Threat_Minimization#Speakers|speaker]] ([[Hardware_Threat_Minimization#Profiling_Threat|profiling threat]]).

=== VirtualBox ===
* Remove a host of [[Virtualization_Platform_Security#VirtualBox Hardening|VirtualBox features]] to reduce the attack surface.
* Take regular, clean [[Virtualization_Platform_Security#VM_Snapshots|VM snapshots]] that are not used for any activities.
* Spoof the initial [[Network_Time_Synchronization#Spoof_the_Initial_Virtual_Hardware_Clock_Offset|virtual hardware clock offset]].
* Consider disabling [[VirtualBox/Guest_Additions#Clipboard_Sharing|clipboard sharing]] to reduce the risk of identity correlation. <ref>Bidirectional clipboard sharing is currently enabled by default in {{project_name_short}} 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.</ref>
* [[VirtualBox/Guest_Additions#Shared_Folder|Shared folders]] are discouraged because they weaken isolation between the guest and the host. <ref>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.</ref>

== Warrant Canary ==

* Learn more about [https://en.wikipedia.org/wiki/Warrant_canary warrant canaries] -- see [[Trust#{{project_name_short}}_Warrant_Canary|{{project_name_short}} Warrant Canary]] ([https://forums.whonix.org/t/whonix-warrant-canary/3208 forum discussion]) and [https://www.eff.org/deeplinks/2016/05/canary-watch-one-year-later limitations of warrant canaries].

= Moderate =

== Create a USB Qube ==

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* Prepare and safely utilize a [https://www.qubes-os.org/doc/how-to-use-usb-devices/ USB qube]. <ref>A USB qube is automatically created as of Qubes R4.0.</ref> <ref>USB keyboards and mice expose dom0 to attacks, and all USB devices are potential [https://en.wikipedia.org/wiki/Side-channel_attack side channel attack vectors].</ref>
* Configure a [https://www.qubes-os.org/doc/disposable-customization/#create-the-sys-usb-disposable disposable <code>sys-usb</code>].

== {{project_name_short}} as a Host Operating System Hardening ==

=== All Platforms ===

* Use [[Full_Disk_Encryption|Full Disk Encryption (FDE)]] on {{project_name_short}}.
* Apply a [[Protection_Against_Physical_Attacks#BIOS_Password|BIOS password]] for BIOS setup and boot.
* Follow all other {{project_name_short}} recommendations to [[Advanced_Host_Security#Key_Hardening_Steps|further harden the host OS]] against [[Protection_Against_Physical_Attacks|physical attacks]].

== Kernels / Kernel Modules ==

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| text    = <u>Note</u>:
* Cutting-edge kernels can destabilize the system or cause boot failures.
* Newer kernels can expose additional vulnerabilities; see footnotes. <ref>[https://grsecurity.net/the_truth_about_linux_4_6 The Truth about Linux 4.6]: <blockquote>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.</blockquote></ref> <ref>{{project_name_short}} contributor madaidan has [https://forums.whonix.org/t/kernel-recompilation-for-better-hardening/7598?page=11 noted]: <blockquote>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.</blockquote></ref>
* Kernel modules in Qubes and {{q_project_name_short}} usually require configuration of a Qubes VM Kernel.
}}

* To benefit from additional protections, <ref>Including [https://grsecurity.net/ grsecurity elements] being mainlined by the [https://web.archive.org/web/20220226010145/https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project Kernel Self Protection Project].</ref> consider installing [[Kernel|newer kernels]].
** On [https://wiki.debian.org/KernelFAQ {{project_name_short}}] as a host and/or VM.
** Qubes: in [https://www.qubes-os.org/doc/how-to-install-software-in-dom0/ dom0] and in Qubes VMs (see [https://www.qubes-os.org/doc/managing-vm-kernels/ Qubes VM Kernel]). <ref>This will likely become the default in future, see: [https://github.com/QubesOS/qubes-issues/issues/5212 Simplify and promote using in-vm kernel].</ref> <ref>Do not raise Qubes VM Kernel issues at {{project_name_short}}. Instead, contact [https://www.qubes-os.org/support/ Qubes support].</ref> <ref>https://forums.whonix.org/t/what-to-post-in-this-qubes-whonix-forum-and-what-not/2275</ref>
* In [[Qubes|{{q_project_name_short}}]], consider installing the [https://github.com/{{project_name_short}}/tirdad tirdad] kernel module to protect against [https://bitguard.wordpress.com/2019/09/03/an-analysis-of-tcp-secure-sn-generation-in-linux-and-its-privacy-issues/ TCP ISN-based CPU information leaks]. <ref>The TCP Initial Sequence Numbers (ISNs) are randomized.</ref> <ref>[https://github.com/{{project_name_short}}/tirdad tirdad] is installed in {{non_q_project_name_long}} by default.</ref>
* Advanced users can undertake [https://madaidans-insecurities.github.io/guides/linux-hardening.html#kernel host kernel hardening] to significantly increase security and privacy.

== Live-mode ==

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* Consider running it in {{project_name_short}}, so all writes go to RAM instead of the hard disk.
* [[Anti-Forensics_Precautions|Disable swap and program crash dumps]] as an anti-forensics precaution.
* When using [[Live Mode]] in a VM consider enabling [[read-only|read-only hard drive mode]] to make it harder for malware to gain persistence. <ref>This prevents remounting of the hard drive as read-write.</ref>

== Networking ==

=== All Platforms ===
* If possible, use a [[Host_Firewall#Dedicated_Connection|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 [[Advanced_Host_Security#DMZ|de-militarized zone]] (perimeter network). <ref>This restricts {{project_name_gateway_short}} accessibility to/from other nodes on the network such as printers, phones and laptops.</ref>
* Test the [[Host_Firewall#Port_Scan|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 [[Passwords#Generating_Unbreakable_Passwords|Diceware passphrase]] to prevent bruteforcing attacks.
* WiFi users should default to the [https://en.wikipedia.org/wiki/Wi-Fi_Protected_Access WPA2-AES] (avoid [https://en.wikipedia.org/wiki/Temporal_Key_Integrity_Protocol#Security TKIP]) or [https://www.wi-fi.org/news-events/newsroom/wi-fi-alliance-introduces-security-enhancements WPA3] standard; the protocols are safer and have stronger encryption. <ref>[https://www.malwarebytes.com/blog/news/2018/01/wpa3-will-secure-wi-fi-connections-in-four-significant-ways-in-2018 WPA3 protocol improvements] 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.
* [https://www.schneier.com/blog/archives/2018/07/wpa3.html Forward secrecy]: if an adversary captures encrypted Wi-Fi transmissions and cracks the password, they cannot use it to read older data.</ref> <ref>Do not rely on WiFi Protected Set-up (WPS), which has [https://en.wikipedia.org/wiki/Wi-Fi_Protected_Setup major security flaws].</ref>
* Follow all other {{project_name_short}} recommendations to [[Router_and_Local_Area_Network_Security#Recommended_Router_Settings|lock down the router]].
* Disable [https://en.wikipedia.org/wiki/TCP_SACK#Selective_acknowledgments TCP Selective Acknowledgement (SACK)] unless it is required, since it is a commonly exploited option in the TCP protocol and not needed for many people; see footnotes. <ref>For example, it has been used for [https://en.wikipedia.org/wiki/SACK_Panic#SACK_Panic remote denial of service attacks] and can even lead to a Linux kernel panic.</ref>  <ref>
{{Box|text=
'''1.''' {{Open with root rights|filename=
/etc/sysctl.d/30_security-misc.conf
}}

'''2.''' Uncomment all lines starting with <code>net.ipv4</code>.

Note: This procedure can also be repeated in {{project_name_gateway_short}}.

TCP SACK is not disabled by default because on some systems it can greatly decrease network performance.
}}</ref> <ref>
https://forums.whonix.org/t/disabling-tcp-sack-dsack-fack/8109/5
</ref>

=== {{q_project_name_short}} Only ===
* Prefer the {{project_name_short}} Template for networking (<code>sys-net</code> and <code>sys-firewall</code>) since it is [https://github.com/QubesOS/qubes-issues/issues/1781 minimal in nature] and does not "ping home", unlike the Fedora Template. <ref>https://forums.whonix.org/t/disable-sys-net-pings-to-fedoraproject-org/1952</ref>
* Consider using customized [https://www.qubes-os.org/doc/templates/minimal/ minimal templates] for NetVMs to reduce the attack surface and memory requirements.

== Sandboxing ==

* Consider using [[Dev/Firejail|Firejail]] to restrict Firefox-ESR, VLC and other regularly used applications -- note this comes with an increased [https://forums.whonix.org/t/tor-browser-hardening-hardened-malloc-firejail-apparmor-vs-web-fingerprint/7851/54 fingerprinting risk] and any vulnerability in Firejail [https://madaidans-insecurities.github.io/linux.html#firejail can allow escalation to root privileges].
* In a future [[{{non_q_project_name_short}}|{{non_q_project_name_short}}]] release, consider using [[Sandbox-app-launcher|<code>sandbox-app-launcher</code> (Sandboxed Application Launcher)]] to restrict applications within a bubblewrap sandbox and confined by AppArmor. <ref>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.</ref>

== security-misc ==
* Consider [[security-misc]]'s [[Security-misc#Optional_Features|Optional Features]].

== Spoof MAC Addresses ==

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| text    = '''Tip:''' [https://en.wikipedia.org/wiki/MAC_spoofing MAC spoofing] is only necessary if traveling with your laptop or PC. It is not required for home PCs that do not change locations.
}}

* In [[Qubes|{{q_project_name_short}}]], [https://github.com/Qubes-Community/Contents/blob/master/docs/privacy/anonymizing-your-mac-address.md follow these steps] to spoof the MAC address on the {{project_name_short}} or Fedora Template used for network connections.
* In [[{{non_q_project_name_short}}|{{non_q_project_name_short}}]], follow [https://www.whonix.org/wiki/MAC_Address#Changing_MAC_Addresses these steps] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/MAC_Address#Changing_MAC_Addresses .onion]) to spoof the MAC address of the network card.

== Time Related ==
* {{non_q_project_name_short}} only: [[Disable_TCP_and_ICMP_Timestamps#Disable_ICMP_Timestamps|Disable ICMP timestamps]] and [[Disable_TCP_and_ICMP_Timestamps#Disable_TCP_Timestamps|TCP timestamps]] on the host operating system to prevent leakage of information. <ref>Such as system information, host time, system uptime, and fingerprinting of devices behind a router.</ref>
* {{non_q_project_name_short}} only: [[Time_Attacks#Mitigations|Uninstall the NTP client]] on the host operating system and disable systemd's timdatectl NTP synchronization feature. <ref>
This prevents time-related attack vectors which rely on leakage of the host time.
</ref>
* Prevent possible time leaks by [[Network_Time_Synchronization#Block_Networking_until_sdwdate_Finishes|blocking networking until sdwdate finishes]].

== Tor Settings ==

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}}

* Consider enabling [https://www.whonix.org/wiki/Whonix-Gateway_Security#Tor_Connection_Padding Tor connection padding] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Whonix-Gateway_Security#Tor_Connection_Padding .onion]) for potentially better protected connection; note it is unclear whether this provides any additional benefit (see footnote). <ref>https://forums.whonix.org/t/tor-connectionpadding/7477</ref>
* Consider installing [[Tor_Versioning|newer Tor versions]].
* Avoid [https://www.whonix.org/wiki/Tor_Entry_Guards#Regenerate_the_Tor_State_After_Saving_the_Tor_State_Folder regenerating the Tor state file] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Tor_Entry_Guards#Regenerate_the_Tor_State_After_Saving_the_Tor_State_Folder .onion]) or [https://www.whonix.org/wiki/Tor_Entry_Guards#Manual_Rotation_of_Tor_Guards manually rotating Tor guards] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Tor_Entry_Guards#Manual_Rotation_of_Tor_Guards .onion]) because it degrades security.
* Avoid configuring [https://www.whonix.org/wiki/Tor_Entry_Guards#Fresh_Tor_Entry_Guards_by_Regenerating_the_Tor_State_File non-persistent entry guards] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Tor_Entry_Guards#Fresh_Tor_Entry_Guards_by_Regenerating_the_Tor_State_File .onion]), as this ''severely'' degrades security.
* Consider using [https://www.whonix.org/wiki/bridges bridges] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Bridges .onion]) if Tor is blocked, dangerous or deemed suspicious in your location.
* If using a bridge, configure [https://www.whonix.org/wiki/Tor_Entry_Guards#Alternating_Bridges alternating bridges] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Tor_Entry_Guards#Alternating_Bridges .onion]) for different physical locations.
* Heavily censored users should configure a ''meek-azure'' bridge. <ref>For example, {{project_name_short}} users residing in China.</ref>

== {{project_name_short}} VM Security ==

* Consider disabling the [https://www.whonix.org/wiki/Whonix-Gateway_Security_Hardening#How-to:_Disable_Control_Port_Filter_Proxy Control Port Filter Proxy] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Whonix-Gateway_Security_Hardening#How-to:_Disable_Control_Port_Filter_Proxy .onion])  to reduce the attack surface on {{project_name_short}}.
* Consider [[systemcheck_Hardening|hardening systemcheck]].
* Consider the periodic deletion and recreation of VMs that are used for sensitive operations.
** If a compromise of {{project_name_short}} is suspected, follow the  [[Disaster_Recovery|compromise recovery]] instructions.

= Difficult =

== Anti-Evil Maid ==

* Consider the Android [https://guardianproject.github.io/haven/ Haven application] for sensitive devices -- motion, sound, vibration and light sensors can monitor and protect physical areas. <ref>Notifications are made in real time for any potentially suspicious activity.</ref>
* If a Trusted Platform Module (TPM) is available, enable it in BIOS/UEFI and [https://paolozaino.wordpress.com/2021/02/21/linux-configure-and-use-your-tpm-2-0-module-on-linux/ configure the required services] to protect against [[AEM|Evil Maid Attacks]].
** {{q_project_name_short}}: Utilize [https://www.qubes-os.org/doc/anti-evil-maid/ AEM protection] to attest that only desired (trusted) components are loaded and executed during the system boot. <ref>Unauthorized modifications to BIOS or the boot partition will be notified.</ref>

== Disposabless ==

{{mbox
| type    = notice
| image   = [[File:Ambox_notice.png|40px|alt=Info]]
| text    = Qubes / {{q_project_name_short}} only. <br /> <u>Note</u>: Some traces of Disposables usage and data contents will leak into the <code>dom0</code> filesystem and survive reboots; see [https://github.com/QubesOS/qubes-issues/issues/4972 here] for further information. (This is a Qubes-specific issue and [[Unspecific|unrelated to {{project_name_short}}.]])
}}

* Run all instances of Firefox in a [https://www.whonix.org/wiki/Qubes/Disposable_VM Disposables] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Qubes/Disposable_VM .onion]) which is preferably uncustomized to resist fingerprinting.
* Configure each ServiceVM as a [https://www.qubes-os.org/doc/disposable-customization/ static Disposables] to mitigate the threat from persistent malware accross VM reboots. <ref>Users can configure <code>sys-net</code>, <code>sys-firewall</code> and <code>sys-usb</code> as static Disposabless. This option has been available from Qubes R4 onward.</ref>

== Email ==

=== All Platforms ===

* Follow the [[E-Mail#Email_Provider_Comparison|{{project_name_short}} recommendations]] to select an email provider compatible with security and privacy.
* Use [https://www.whonix.org/wiki/Encrypted_Email_with_Thunderbird Mozilla Thunderbird] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/Encrypted_Email_with_Thunderbird .onion]) as an email client. <ref>Reminder: The ''Subject:'' line and other header fields are <u>not</u> encrypted in the current configuration.</ref>
* For greater email or message security, consider using the [[PQCrypto#OneTime|OneTime]] application or a [https://www.whonix.org/wiki/One_Time_Pad physical one-time pad] ([http://dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/wiki/One_Time_Pad .onion]) for military-grade encryption.
* Follow all other [[E-Mail#Safe_Email_Principles|email principles for greater safety]].

=== {{q_project_name_short}} Only ===

* Use [https://www.qubes-os.org/doc/split-gpg/ split-GPG] 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 [https://micahflee.com/2016/07/how-qubes-makes-handling-pdfs-way-safer/ untrusted email attachments] in a Disposables to prevent possible infection.

== Ethernet/FDDI Station Activity Monitor ==

* Consider running [https://packages.debian.org/{{Stable project version based on Debian codename}}/arpon ArpON] as a daemon to defend against ARP attacks like [https://web.archive.org/web/20230330072313/https://fossbytes.com/arp-spoofing-attacks-detection-prevention/ ARP spoofing], [https://www.techopedia.com/definition/27471/address-resolution-protocol-poisoning-arp-poisoning ARP cache poisoning] and [https://networklessons.com/switching/arp-poisoning ARP poison routing]. <ref>Attackers use these methods to redirect local network traffic and execute [[Warning#Man-in-the-middle_Attacks|Man-in-the-middle Attacks]].</ref>
* Consider utilizing [https://packages.debian.org/{{Stable project version based on Debian codename}}/arpwatch Arpwatch] to be alerted about any changes to the database of Ethernet MAC addresses seen on the network. <ref>Administrators are advised of any changes via email, such as new station/activity, flip-flops and re-used/changed old addresses.</ref>

== Flash the Router with Opensource Firmware ==

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| image   = [[File:Ambox_warning_pn.svg.png|40px]]
| text    = '''Warning:''' risk of bricking your router!
}}

* Flash the insecure, limited-utility, proprietary firmware on the router with a [[Router_and_Local_Area_Network_Security#Router_Firmware|powerful, open-source GNU/Linux alternative]].

== Multi-Factor User Authentication ==

* Set up [[Two-factor_authentication_2FA|two-factor authentication (2FA)]] to strengthen the security of online accounts, smartphones, web services, access to physical locations and other implementations.
* Configure [https://wiki.debian.org/pamusb PAM USB] 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 [https://www.nitrokey.com/ Nitrokey] hardware authentication device which supports one-time passwords, public-key encryption, and the Universal 2nd Factor (U2F) and FIDO2 protcols.
** Qubes: Follow the [https://www.qubes-os.org/doc/mfa/ NitroKey/YubiKey] to enhance the security of Qubes user authentication, mitigate the risk of password snooping, and to improve USB keyboard security.

== Systemd Sandboxing ==

* Create drop-in <code>.conf</code> files to [https://git.sr.ht/~krathalan/systemd-sandboxing sandbox systemd services].

= Expert =

== Disable Intel ME Functionality ==

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| image   = [[File:Ambox_warning_pn.svg.png|40px]]
| text    = '''Warning:''' high risk of bricking your computer!
}}

* It is possible to [https://hardenedlinux.github.io/firmware/2016/11/17/neutralize_ME_firmware_on_sandybridge_and_ivybridge.html partially deblob] Intel's despicable ME firmware image by [https://github.com/corna/me_cleaner/blob/master/me_cleaner.py removing unnecessary partitions] from it.
* Alternatively, [[Out-of-band_Management_Technology#Hardware|Intel ME's "High-Assurance Platform" mode]] can be set manually to disable most ME capabilities.

== Disable SUID-enabled Binaries ==

{{mbox
| type    = notice
| image   = [[File:Ambox_notice.png|40px|alt=Info]]
| text    = This is an experimental feature recommended for testers.
}}

* Consider enforcing the [[SUID_Disabler_and_Permission_Hardener|SUID Disabler and Permission Hardener]] to increase the security of the system; see [[Security-misc#SUID_Disabler_and_Permission_Hardener|here]] for instructions. <ref>This reduces the attack surface by disabling SUID-enabled binaries and improves [[Dev/Strong_Linux_User_Account_Isolation|Strong Linux User Account Isolation]]. Some SUID binaries have a history of privilege escalation security vulnerabilities. This feature is part of [[security-misc]].</ref>

== Opensource Firmware ==

* [https://libreboot.org/ Libreboot] is no longer recommended as a proprietary firmware alternative; see footnote. <ref>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 {{project_name_short}} population.</ref>
* [https://www.coreboot.org/ Coreboot] is a possible BIOS/UEFI firmware alternative -- consider [[Open-source_Hardware#Buyer_Considerations|purchasing hardware]] that has it pre-installed (like Chromebooks), or research flashing procedures for the handful of refurbished motherboards that support it.
** <u>Note</u>: The open Qubes ticket on [https://github.com/QubesOS/qubes-issues/issues/1594 Research support for libreboot/coreboot-based systems] makes the opensource firmware recommendation generally unsuitable for {{q_project_name_short}} at present.
** <u>Exception</u>: Several laptops meet [https://www.qubes-os.org/doc/certified-hardware/ Qubes' Certified Hardware] requirements and are configured with Coreboot, Heads and a partially disabled Intel Management Engine.

= Footnotes =
{{reflist|close=1}}

{{Footer}}

[[Category:Documentation]]