Tag Archives: Security

TLDR Digital Safety Checklist

🤔 Who this guide is for

  • You use the internet on a day-to-day basis – for work, social media, financial transactions, etc.
  • You feel you could be doing more to ensure your digital safety and privacy, but you’re also not in immediate danger. (If you are, seek out an expert for a 1:1 consult.)
  • You’re comfortable with technology. For example, you’re comfortable going into the settings section of your computer/smartphone.

🌱 How this guide works

  • Recommendations have been sorted in ascending levels of difficulty. Start from level one and work your way up!
  • I recommend doing everything in levels one, two and three. I did, and I’m only a mildly technically-competent person.
  • Then scan the scenarios to see if any of them apply to you. (They assume that you’ve done everything in levels 1-3.)
  • This guide is a living document – please feel free to submit a pull request or fork your own version of this guide on GitHub.

🕒 Last updated

  • 23 October 2019

🧐 Theory & science

🎯 Threat modeling

  • What kind of danger are you in? E.g. corporate espionage, police/state intervention, online harassment/doxxing.
  • What kind of assets are you protecting? E.g. confidential documents, private photos.
  • We’re all in a little bit of danger (otherwise we wouldn’t bother putting a password on our computer or phone) but it’s important to think about what’s at stake before dismissing concerns or becoming paranoid.
  • For more info, read the EFF’s introduction to threat modeling.
  • Remember the weakest link is all that matters! E.g. if password recovery is linked to email, then hackers only need to get access to your email.

🔡 Encryption levels

  1. Not encrypted: Any third party who intercepts the data can read it as-is.
  2. Regular encryption: Data is encrypted so that third parties cannot read them. But the platform (e.g. Google or Facebook) still has access, and may hand the data over to law enforcement if they are required to do so by the courts/the government.
  3. End-to-end encryption: the data can only be read by the original sender and receiver. This means not even the platform has access. So if law enforcement calls, the service provider can’t hand over the messages because they don’t have them either.

🧩 Metadata

  • Data about your data – e.g. what number you called, and for how long (but not the contents of the call). With enough metadata, hackers can piece together a pretty good picture of who you are, who you know, where you’re going, etc. Plus legal protections around metadata are generally weaker.

💦 Level 1 recommendations

✅ Things to do now


  • If you’re on a webmail service, check that you’re logging into it using an https:// URL. And if there isn’t one, find a new email provider.
  • Turn on two-factor authentication for your email service (e.g. instructions for Gmail, Protonmail) if they support an authenticator app (SMS is no longer considered safe) (e.g. Authy, Google Authenticator).
  • After turning on two-factor authentication, see if your email service supports backup codes (a single-use code in case you lose your phone). See Gmail instructions.

Good passwords

  • Any password less than 10 characters is bad, but it’s also okay-to-string-together-non-sequitur-words.
  • Double check the security questions for your key online services (email, bank, Facebook, etc.) and make sure that they’re not easy to answer by friends/looking you up on Google.
  • Start using a different password for every service, because password leaks happen all the time. To make this easy, use a password manager (Lifehacker reviews them here) to store/autofill/generate them. For now, make sure you use a unique password for essential services (email, social media, banking, cloud storage).
  • Use a non-common/obvious unlock code for your phone.
  • On iPhone, turn off USB Accessories in Settings > Face ID & Passcode > Allow Access When Locked.

Encrypt your devices

  • Encrypt your phone storage: Android, iOS (many phones now encrypt by default but it’s worth double checking).
  • Encrypt your laptop/desktop hard drive: Windows, Windows if no BitLocker, Mac OSX.
  • Secure your backups too! Encrypt your backup hard drives and/or make sure your online backup storage solution supports end-to-end encryption.
  • N.B. Remember encryption is only fully effective when the device is off!


💪🏽 Habits to cultivate


  • Be on the lookout for phishing scams: where possible double check the From email address and the domains that outbound links go to.
  • Don’t open unnecessary email attachments. Where possible, open/preview them first in an online document reader, or have colleagues use a filesharing server or service (Dropbox, Google Drive, SpiderOak, Tresorit), which tend to be a little harder to hack into.
  • You can upload a suspicious attachment to VirusTotal for a check-up (but keep in mind files submitted to VirusTotal are available to security researchers so don’t submit sensitive information).

Update all the things

  • When you get a notification to update your operating system (on your mobile or computer), do it right away.
  • Same for apps (mobile + computer).
  • Check occasionally for firmware updates for your router (and other Internet-connected devices).


  • Change important passwords (e.g. email, computer login, password manager master) every year or two.
  • Wipe your devices properly before donating/giving away: phone, computer.
  • Don’t charge your phone at public charging stations/ports – they may steal your data. Consider charging your portable battery instead.

👍 Great job! You’ve covered the basics.
👍 What about trying out the next level?

💦💦 Level 2 recommendations

✅ Things to do now

Enhance your privacy

  • Review the privacy settings on social networks you frequent: who can see your content, who can comment on it, and who can see your location.
  • Install these protective web browsers add-ons (and make sure they’re on even during private/incognito mode):
  • If you use smart speakers, turn off its recording function: instructions for Google Home and for Amazon Alexa.


  • Set up your devices with third-party applications (e.g. Prey, Lookout Security so you can remotely track, wipe, and encrypt your devices from a website in the future.
  • Review what’s connected to your main email/social media accounts (e.g. what kinds of services have access to Facebook, and what data can they access and/or can they post on your behalf).
  • Review the extensions/add-ons/plug-ins that have been installed within your computer web browser – delete any that you haven’t used in a while or don’t remember installing.
  • Download and run Stethoscope for your computer, which make sure your basic security settings (encryption, firewall, screen locks, etc.) are covered.

💪🏾 Habits to cultivate

Enhance your privacy

  • Post less personal information online – especially information that can be used to identify/track/scam you (addresses, phone numbers, birthday, etc.). Remember almost everything you say online is logged somewhere and that even if your setup is secure, your recipient’s setup may not be.
  • Buy a privacy screen (prevents onlookers from seeing your screen, see this 3M example) for your laptop and/or phone.
  • If you own domains, use WHOIS privacy services and stick with it (they’re worth the money). But note that with WHOIS lookup/history tools, if you’ve ever put in your real address, it’s very difficult to remove from the logs.


  • Use a paid VPN service when on public networks (e.g. cafe wifi) – free VPN services are bad because operators don’t have enough incentive to protect you/your data. See recommendations from Wirecutter and Freedom of the Press.
  • Check what apps you have installed on your phone once in a while, and delete the ones you’re not using anymore.
  • If you ever need to send someone a password, split it in half and send via two different channels (e.g. email + voice call).
  • Put a sticker (or webcam cover) over your laptop’s front-facing camera.
  • Don’t use Google/Twitter/Facebook to sign up/login to other services – each service should have its own account.

🎉 Congratulations! You’re now reasonably
🎉 secure, which is more than most 🙂

💦💦💦 Level 3 recommendations

✅ To do

Lock up sensitive files

  • Identify files that you don’t want others to access (e.g. private photos, passport documents).
  • Use Cryptomator or Veracrypt to create an encrypted, password-protected vault for them.
  • Set them up on both your desktop/laptop and your phone.
  • Move your files into these secure vaults. Make sure they’re not still hanging around on an old folder or on your phone.

Revisit old passwords

  • Store all of your online service passwords in a password manager. (If you have the right browser add-on/plugin installed, it will capture all the relevant details during a login process.)
  • Using your password manager’s analysis feature, see which accounts/services have weak passwords and update the ones that might have any personal information about you or that you would really hate to lose.

💪🏾 Habits to cultivate

  • Start using Signal, an end-to-end encrypted mobile messaging app that’s generally agreed to be safe/secure/robust. (Beyond Signal, there is little consensus on what’s secure and people tend to get very emotional about their choice of mobile messaging apps.)
  • When making voice or video calls, use an end-to-end encrypted app (e.g. Signal, Jitsi, Wire).
  • Buy a harder-to-hack mobile phone ($$$). Typically, this is an iPhone or Android phone that implements a “pure” Google version of Android.

😲 Wow, you even finished the difficult
😲 digital housekeeping tasks. Well done!

💦❗️ Scenario-based recommendations

🛫 Crossing an international border

  • Turn off your devices because:
    • Storage/hard drives are only encrypted when they’re off, not when they’re just in sleep mode
    • This will also ensure that your mobile devices require a pin when they are turned on, which is protected by freedom of speech laws in some jurisdictions.
  • Store less information on your devices – in case they’re seized, what you don’t have they can’t take.
  • Be mindful of what stickers you put on your devices – a border agent could mistake them for something suspicious.
  • Notify your people about your flight number and arrival time. Have them contact a lawyer/relevant organization if you do not show up.
  • For high risk situations (some of these practices might raise suspicions and backfire):
    • Set up alternate photo albums, email addresses and social media accounts full of harmless content.
    • “Forget” half of your password: Password lock your device/account so that only a trusted friend has the second half of the password.
    • Log out of all important accounts (or simply leave your devices at home).
  • For more information, see Wired’s Guide to Getting Past Customs With Your Digital Privacy Intact and BoingBoing’s addendum about filing for attorney privileges at the US border.

😭 Somebody took my phone/computer!

  • Wipe your phone remotely: see instructions for Android, iOS.
  • Log out of all important accounts from another device.
  • If this happened at an international border: Ask for a seizure receipt (available in some jurisdictions, e.g. Canada)
  • Get a new SIM card.
  • If you get it back, reset your phone/computer back to its factory settings. Then run some anti-virus and anti-spyware programs just in case.

👾 I think my computer has been hacked!

  • Download an application that will notify you when data is being sent out from your computer. E.g. Little Snitch for Mac.
  • Run Activity Monitor on Mac or Process Explorer on Windows to look at what processes/applications are running. Google any suspicious names.
  • Login to important online accounts to see if there have been any suspicious logins – see this Motherboard guide for details.
  • Setup a spare smartphone using Haven as a room monitor to detect unwanted intrusions.

🍆 Sexting & non-consensual image sharing

✊🏾 Attending a protest

In case of emergency

  • Draft a message to a trusted friend (not at protest) or legal hotline. Be ready to hit send if you are arrested/there is an emergency.
  • Bring a spare battery for your phone.
  • If you use thumbprint (or facial recognition) unlock, immediately power off your phone if you’re ever arrested. In some jurisdictions, officers can compel you to provide your fingerprint but not your passcode. Better yet, turn off fingerprint or face ID before going to a protest.
  • If you’re attending a high-risk protest: leave your phone at home or use burner phone.

Store less share less

  • Keep as little sensitive personal information or incriminating information as possible – you never know whose hands it might end up in.
  • Turn on disappearing messages if your messaging app supports it.
  • If you need to share photos, erase the associated metadata first using these apps.
  • Turn off location history:
    • iPhone: Settings > Privacy > Location Services > System Services > Significant Locations
    • Android: Settings > Google > Google Account > Data & personalization > Location History > Manage setting > Your account & all your devices > turn off Use Location History
    • Google Maps: Settings > Maps history > Web & App Activity
  • Delete past location history:
    • iPhone: Settings > Privacy > Location Services > System Services > Significant Locations > Clear History
    • Android
    • Google Maps


  • Double check your messaging apps privacy settings.
  • Turn off message previews in your notifications:
    • iOS: Settings > Notifications > Show Previews: When Unlocked
    • Android: Settings > Apps & notifications > Notifications > On lock screen: Hide sensitive content
  • Remember to make voice calls through end-to-end encrypted apps like Signal or Whatsapp.
  • More info from the EFF about protesting in the US and internationally.

📰 I’m a journalist working on a sensitive topic

Below are some basics that all journalists should consider. If you’re working on/in a particularly sensitive story/region (e.g. a whisteblower story in the US or China), you and your team should get an tailored training session from an expert.

Be prepared

  • To remotely wipe the contents of your devices using a tracking app (e.g. Find My on iOS, Find My Device on Android, Prey, Lookout Security).
  • To be on the receiving end of an email phishing campaign (as journalist emails are usually more public than others).

Protect yourself

  • If you’re traveling, review the Crossing an international border scenario above.
  • If you’re covering a protest, review the Attending a protest scenario above and decide which parts apply to you (if you have special journalist rights/protections where you’re working).
  • Use a VPN if you’re browsing the internet at the office (website administrators can usually see that you’re coming from, say, the New York Times network)

Protect your sources

Protect your data

  • Make sure you’re using an email/storage provider that’s not owned/linked to a state or organization that you’re reporting on.
  • Better yet, move all of your work onto end-to-end encrypted platforms. (E.g. Protonmail Be aware that courts can compel Google to hand over all of your data.
  • Store sensitive data in a password-protected cloud or external storage device as much as possible. See the Lock up sensitive files section above.
  • Remember to permanently erase sensitive files from your laptop/desktop: use Eraser for Windows and File Shredder for Mac.

For more information

🕵🏼‍♂️ Online harassment & doxxing

Harassment and doxxing can get very specific and complicated based on the attacker, your position, the overall cultural context, etc. While we have some general suggestions below, we implore you to think about whether your situation has escalated sufficiently and whether it’s time to find professional, one-on-one help.

Recruit a trusted friend

  • Do not force yourself into a corner by going at this alone!
    • Baseline: Ask a trusted friend to hold space for your situation and be your sounding board on analyzing how bad the threat is.
    • Preferred: Ask a trusted friend to help you investigate, record, report and block harassers – see Take Back The Tech’s Hey Friend! guide for more details about this. In some cases, it may be healthier to hand over your phone/social media/accounts over to them so that you’re not constantly triggered.
  • Alternately, reach out to online communities you’re an active member of and ask for help. See PEN America’s article on Deploying Your Supportive Cyber Communities.
  • If no one is available right now, Heartmob has a list of supportive organizations, some of which have 24/7 hotlines.

Monitor updates & collect receipts

  • Set up a Talkwalker and/or Google Alerts for your name/nickname.
  • Start logging (date, time, description, screenshot) incidents in whatever program/app that’s easiest for you.

Remove your personal information from the internet

  • Pay PrivacyDuck to scrub your information online. If you are an activist you can contact Equity Labs for a discounted rate.
  • Pay Reputation.com to remove your information from paid sites and monitor them to make sure it stays removed.
  • Alternately, both PrivacyDuck and Motherboard have free online resources to help you remove your information yourself.

Obscure your personal information

  • Use Burner to set up burner phone numbers for calling/texting.
  • Use Traveling Mailbox to obscure your postal address.
  • Delete old accounts to eliminate traces of personal information on the Internet. Use Justdelete.me to accelerate this process.
  • Review your social media accounts and delete any posts that reveal too much about where you live/where you go/who you’re with.
  • For Twitter users:
    • Ask around in your communities for shared block lists of known offenders.
    • Use Semiphemeral to delete most of your unwanted posts on Twitter. (Requires use of the command line.)

Ignore/reply/report/block your harassers

  • Together with your support person/friend and the log of receipts, decide on your course of action (these aren’t mutually exclusive):
    • Ignore: Sometimes harassers will walk away if they don’t get attention.
    • De-escalate: In some contexts, you can defuse the situation with some calm words before it gets worse.
    • Report: Report the harasser to the relevant online platform and/or your local law enforcement.
    • Mute on social media: Allows for peace of mind.
    • Block on social media: Maximizes peace of mind as the harasser won’t be able to see your posts. But they will notice and see it as a sign of escalation.
    • Go public: Can be dangerous, but sometimes shaming them publicly or rallying people to your support will make them go away.

For more information

👤 I don’t want to give out my real phone number for online dating/networking/organizing

For messaging apps that use phone numbers as the primary identifier/username (e.g. Signal, WhatsApp), get a secondary number from:

  • Twilio (1 USD/month, but complicated setup – see the Twilio section here and this guide)
  • Burner (5 USD/month, but also has prepaid plans for short-term use)
  • Google Voice (free but only available in the US)
  • A phone company: get a prepaid or cheap SIM card plan (rates vary)

But keep in mind:

  • If you lose/unsubscribe to your secondary phone number, other people can buy it and impersonate you.
  • Most companies will still hand over your information to the authorities if the latter files the right paperwork.

For true anonymity – create an untraceable online persona under a pseudonymn

💦❓ Other recommendations

This section is a catch-all for difficult or esoteric practices that do not fall under any of our scenarios above and might not have any immediate payoff for the casual user.



File storage & sharing

  • Use an end-to-end encrypted cloud storage service (not Dropbox): Tresorit, SpiderOak.
  • Use encrypted external USB/hard drives from companies like Apricorn.
  • If you want to send a file anonymously, use a special sharing service like OnionShare.
  • Instead of Google Docs or Microsoft Office, use CryptPad (open-source, end-to-end encrypted).

Messaging apps

  • WhatsApp additional settings:
    • To be 100% end-to-end encrypted, turn off chat backups on WhatsApp (Settings > Chats > Chat backup) and delete your previous backups (instructions for iOS, Android).
    • Turn on security notifications on WhatsApp (Settings > Account > Security).
    • Set up a pin number to prevent your account from being moved without your permission (Settings > Account > Two-Step Verification).
  • If you’re a journalist who uses Signal regularly, step up your safety practices try following Martin Sheldon’s Locking Down Signal guide (or similarly for WhatsApp if you use that a lot).


  • Keep less information/data/photos on your devices – you can’t lose what you don’t have!
  • Don’t use smart TVs or smart speakers.
  • Search the web anonymously with DuckDuckGo.
  • If you (or your organization) is really wedded to the Google Suite, consider Google’s Advance Protection program.
  • Put your smart cards/passports/phones in a Faraday bag that blocks signals from going in and out. (See Micah Lee’s guide on them.)
  • Fortify your self-hosted WordPress website with Cloudflare + iThemes Security.
  • Use a more secure operating system: Tails (works off of a USB stick) or Qubes OS.
  • For Android users: Download apps using F-Droid, an open-source, security-focused app store.
  • For US residents: Freeze your credit to prevent hackers from accessing sensitive data. See Security Checklist’s Freeze Your Credit section for details.

🏆 Oh my, you made it this far.
🏆 You are a true champ!

🧠 Sources

We consulted many sources and drew upon our own experiences in creating this resource. (See our full list of sources.) If you’re not finding quite what you want here, we recommend checking out these other resources:

For a curated selection, check out Martin Shelton’s Current Digital Security Resources guide.

📝 License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.tldr-digital-security is maintained by hongkonggong.

This article originally appeared on hongkonggong

Hackers Can Add, Remove Cancer From CT Scans: Researchers

By Eduard Kovacs on April 05, 2019

A team of researchers has demonstrated that hackers can modify 3D medical scans to add or remove evidence of a serious illness, such as cancer.

Experts from the Ben-Gurion University and the Soroka University Medical Center, Beer-Sheva, in Israel have developed proof-of-concept (PoC) malware that uses a machine learning technique known as generative adversarial network (GAN) to quickly alter 3D images generated during a Computer Tomography (CT) scan.

CT scanners are typically managed through a picture archiving and communication system (PACS) that receives scans from the scanner, stores them and then supplies them to radiologists. Data is transmitted and stored using a standard format named DICOM. PACS products are provided by companies such as GE Healthcare, Fujifilm, Philips and RamSoft.

One problem, according to researchers, is that PACS and DICOM servers are often left exposed to the internet. A scan conducted using the Shodan search engine identified nearly 2,700 servers that were connected to the internet. Another issue is that the medical imagery data is in many cases transmitted over the network without being encrypted, which exposes it to man-in-the-middle (MitM) attacks and manipulation.

Malicious actors could directly target PACS that are accessible from the Internet, or they could first gain access to the targeted organization’s network and launch the attack from there. Another attack vector, which the researchers tested during a penetration test conducted in a hospital’s radiology department, involves physically connecting a small MitM device between the CT scanner’s workstation and the PACS network. In these local attacks, the attacker can rely on insiders or they can pose as a technician, the researchers said.

Once the attacker can intercept traffic from the CT scanner, they can use an attack framework, which the researchers have dubbed CT-GAN, to manipulate the images via the GAN technique before they reach the radiologist who interprets the results.

CT-GAN attack

The experts have tested the efficiency of the attack by asking three radiologists to diagnose a mix of 30 authentic CT scans and 70 scans altered using CT-GAN. The malware was used to inject evidence of malign cancer into the scans of healthy patients and remove cancer from the scans of patients who actually had it.

When the radiologists were unaware that the results had been manipulated, they diagnosed 99% of the injected scans as cancer and 94% of the scans from which the cancer was removed as belonging to healthy patients. After they were informed of the attack, the radiologists still misdiagnosed the patients in 60% and 87% of cases, respectively. The researchers said the attack even fooled a state-of-the-art lung cancer screening model in each and every one of the tests.

So why would someone want to launch such an attack? The researchers have listed several possible motivations and goals. They believe that modifying someone’s scan and causing a misdiagnosis can be useful for stealing someone’s job, altering elections, sabotaging or falsifying research, earning money by holding data hostage, insurance fraud, and even murder or terrorism.

They pointed out that the method can be used to add or remove evidence of various illnesses, including aneurysms, heart disease, blood clots, infections, arthritis, cartilage problems, torn ligaments, and tumors in the brain, heart or spine.

For example, if an attacker adds evidence of cancer to a political candidate’s CT scan, they can get the targeted individual to withdraw from the race. The same technique could work for getting someone to give up a job or a leadership role. In the worst case scenario, hackers could remove evidence of a serious illness, which could lead to that person dying due to not receiving the proper treatment.

CT-GAN attack motives

The researchers have published a paper detailing their findings, along with a video showing how an attacker could plant a malicious device inside a healthcare organization.

This article originally appeared on SecurityWeek