A Guide to Common Types of Two-Factor Authentication on the Web



  • Two-factor authentication (or 2FA) is one of the biggest-bang-for-your-buck ways to improve the security of your online accounts. Luckily, it’s becoming much more common across the web. With often just a few clicks in a given account’s settings, 2FA adds an extra layer of security to your online accounts on top of your password.

    In addition to requesting something you know to log in (in this case, your password), an account protected with 2FA will also request information from something you _have (_usually your phone or a special USB security key). Once you put in your password, you’ll grab a code from a text or app on your phone or plug in your security key before you are allowed to log in. Some platforms call 2FA different things—Multi-Factor Authentication (MFA), Two Step Verification (2SV), or Login Approvals—but no matter the name, the idea is the same: Even if someone gets your password, they won’t be able to access your accounts unless they also have your phone or security key.

    There are four main types of 2FA in common use by consumer websites, and it’s useful to know the differences. Some sites offer only one option; other sites offer a few different options. We recommend checking twofactorauth.org to find out which sites support 2FA and how, and turning on 2FA for as many of your online accounts as possible. For more visual learners, this infographic from Access Now offers additional information.

    Finally, the extra layer of protection from 2FA doesn’t mean you should use a weak password. Always make unique, strong passwords for each of your accounts, and then put 2FA on top of those for even better log-in security.

    SMS 2FA

    When you enable a site’s SMS 2FA option, you’ll often be asked to provide a phone number. Next time you log in with your username and password, you’ll also be asked to enter a short code (typically 5-6 digits) that gets texted to your phone. This is a very popular option for sites to implement, since many people have an SMS-capable phone number and it doesn’t require installing an app. It provides a significant step up in account security relative to just a username and password.

    There are some disadvantages, however. Some people may not be comfortable giving their phone number—a piece of potentially identifying information—to a given website or platform. Even worse, some websites, once they have your phone number for 2FA purposes, will use it for other purposes, like targeted advertising, conversion tracking, and password resets. Allowing password resets based on a phone number provided for 2FA is an especially egregious problem, because it means attackers using phone number takeovers could get access to your account without even knowing your password.

    Further, you can’t log in with SMS 2FA if your phone is dead or can’t connect to a mobile network. This can especially be a problem when travelling abroad. Also, it’s often possible for an attacker to trick your phone company into assigning your phone number to a different SIM card, allowing them to receive your 2FA codes. Flaws in the SS7 telephony protocol can allow the same thing. Note that both of these attacks only reduce the security of your account to the security of your password.

    Authenticator App / TOTP 2FA

    Another phone-based option for 2FA is to use an application that generates codes locally based on a secret key. Google Authenticator is a very popular application for this; FreeOTP is a free software alternative. The underlying technology for this style of 2FA is called Time-Based One Time Password (TOTP), and is part of the Open Authentication (OATH) architecture (not to be confused with OAuth, the technology behind “Log in with Facebook” and “Log in with Twitter” buttons).

    If a site offers this style of 2FA, it will show you a QR code containing the secret key. You can scan that QR code into your application. If you have multiple phones you can scan it multiple times; you can also save the image to a safe place or print it out if you need a backup. Once you’ve scanned such a QR code, your application will produce a new 6-digit code every 30 seconds. Similar to SMS 2FA, you’ll have to enter one of these codes in addition to your username and password in order to log in.

    This style of 2FA improves on SMS 2FA because you can use it even when your phone is not connected to a mobile network, and because the secret key is stored physically on your phone. If someone redirects your phone number to their own phone, they still won’t be able to get your 2FA codes. It also has some disadvantages: If your phone dies or gets stolen, and you don’t have printed backup codes or a saved copy of the original QR code, you can lose access to your account. For this reason, many sites will encourage you to enable SMS 2FA as a backup. Also, if you log in frequently on different computers, it can be inconvenient to unlock your phone, open an app, and type in the code each time.

    Push-based 2FA

    Some systems, like Duo Push and Apple’s Trusted Devices method, can send a prompt to one of your devices during login. This prompt will indicate that someone (possibly you) is trying to log in, and an estimated location for the login attempt. You can then approve or deny the attempt.

    This style of 2FA improves on authenticator apps in two ways: Acknowledging the prompt is slightly more convenient than typing in a code, and it is somewhat more resistant to phishing. With SMS and authenticator apps, a phishing site can simply ask for your code in addition to your password, and pass that code along to the legitimate site when logging in as you. Because push-based 2FA generally displays an estimated location based on the IP address from which a login was originated, and most phishing attacks don’t happen to be operated from the same IP address ranges as their victims, you may be able to spot a phishing attack in progress by noticing that the estimated location differs from your actual location. However, this requires that you pay close attention to a subtle security indicator. And since location is only estimated, it’s tempting to ignore any anomalies. So the additional phishing protection provided by push-based 2FA is limited.

    Disadvantages of push-based 2FA: It’s not standardized, so you can’t choose from a variety of authenticator apps, and can’t consolidate all your push-based credentials in a single app. Also, it requires a working data connection on your phone, while Authenticator apps don’t require any connection, and SMS can work on an SMS-only phone plane (or in poor signal areas).

    FIDO U2F / Security Keys

    Universal Second Factor (U2F) is a relatively new style of 2FA, typically using small USB, NFC or Bluetooth Low Energy (BTLE) devices often called “security keys.” To set it up on a site, you register your U2F device. On subsequent logins, the site will prompt you to connect your device and tap it to allow the login.

    Like push-based 2FA, this means you don’t have to type any codes. Under the hood, the U2F device recognizes the site you are on and responds with a code (a signed challenge) that is specific to that site. This means that U2F has a very important advantage over the other 2FA methods: It is actually phishing-proof, because the browser includes the site name when talking to the U2F device, and the U2F device won’t respond to sites it hasn’t been registered to. U2F is also well-designed from a privacy perspective: You can use the same U2F device on multiple sites, but you have a different identity with each site, so they can’t use a single unique device identity for tracking.

    The main downsides of U2F are browser support, mobile support, and cost. Right now only Chrome supports U2F, though Firefox is working on an implementation. The W3C is working on further standardizing the U2F protocol for the web, which should lead to further adoption. Additionally, mobile support is challenging, because most U2F devices use USB.

    There are a handful of U2F devices that work with mobile phones over NFC and BTLE. NFC is supported only on Android. On iOS, Apple does not currently allow apps to interact with the NFC hardware, which prevents effective use of NFC U2F. BTLE is much less desirable because a BTLE U2F device requires a battery, and the pairing experience is less intuitive that tapping an NFC device. However, poor mobile support doesn’t mean that using U2F prevents you from logging in on mobile. Most sites that support U2F also support TOTP and backup codes. You can log in once on your mobile device using one of those options, while using your phishing-proof U2F device for logins on the desktop. This is particularly effective for mobile sites and apps that only require you to log in once, and keep you logged in.

    Lastly, most other 2FA methods are free, assuming you already have a smartphone. Most U2F devices cost money. Brad Hill has put together a review of various U2F devices, which generally cost USD $10-$20. GitHub has written a free, software-based U2F authenticator for macOS, but using this as your only U2F device would mean that losing your laptop could result in losing access to your account.

    Bonus: Backup Codes

    Sites will often give you a set of ten backup codes to print out and use in case your phone is dead or you lose your security key. Hard-copy backup codes are also useful when traveling, or in other situations where your phone may not have signal or reliable charging. No matter which 2FA method you decide is right for you, it’s a good idea to keep these backup codes in a safe place to make sure you don’t get locked out of your account when you need them.

    https://www.eff.org/deeplinks/2017/09/guide-common-types-two-factor-authentication-web


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Tmux Commands

screen and tmux

A comparison of the features (or more-so just a table of notes for accessing some of those features) for GNU screen and BSD-licensed tmux.

The formatting here is simple enough to understand (I would hope). ^ means ctrl+, so ^x is ctrl+x. M- means meta (generally left-alt or escape)+, so M-x is left-alt+x

It should be noted that this is no where near a full feature-set of either group. This - being a cheat-sheet - is just to point out the most very basic features to get you on the road.

Trust the developers and manpage writers more than me. This document is originally from 2009 when tmux was still new - since then both of these programs have had many updates and features added (not all of which have been dutifully noted here).

Action tmux screen
start a new session tmux OR
tmux new OR
tmux new-session
screen
re-attach a detached session tmux attach OR
tmux attach-session
screen-r
re-attach an attached session (detaching it from elsewhere) tmux attach -d OR
tmux attach-session -d
screen -dr
re-attach an attached session (keeping it attached elsewhere) tmux attach OR
tmux attach-session
screen -x
detach from currently attached session ^b d OR
^b :detach
^a ^d OR
^a :detach
rename-window to newname ^b , <newname> OR
^b :rename-window <newn>
^a A <newname>
list windows ^b w ^a w
list windows in chooseable menu ^a "
go to window # ^b # ^a #
go to last-active window ^b l ^a ^a
go to next window ^b n ^a n
go to previous window ^b p ^a p
see keybindings ^b ? ^a ?
list sessions ^b s OR
tmux ls OR
tmux list-sessions
screen -ls
toggle visual bell ^a ^g
create another window ^b c ^a c
exit current shell/window ^d ^d
split window/pane horizontally ^b " ^a S
split window/pane vertically ^b % ^a |
switch to other pane ^b o ^a <tab>
kill the current pane ^b x OR (logout/^D)
collapse the current pane/split (but leave processes running) ^a X
cycle location of panes ^b ^o
swap current pane with previous ^b {
swap current pane with next ^b }
show time ^b t
show numeric values of panes ^b q
toggle zoom-state of current pane (maximize/return current pane) ^b z
break the current pane out of its window (to form new window) ^b !
re-arrange current panels within same window (different layouts) ^b [space]
Kill the current window (and all panes within) ^b killw [target-window]
  • Criteo is an ad company. You may not have heard of them, but they do retargeting, the type of ads that pursue users across the web, beseeching them to purchase a product they once viewed or have already bought. To identify users across websites, Criteo relies on cross-site tracking using cookies and other methods to follow users as they browse. This has led them to try and circumvent the privacy features in Apple’s Safari browser which protects its users from such tracking. Despite this apparently antagonistic attitude towards user privacy, Criteo has also been whitelisted by the Acceptable Ads initiative. This means that their ads are unblocked by popular adblockers such as Adblock and Adblock Plus. Criteo pays Eyeo, the operator of Acceptable Ads, for this whitelisting and must comply with their format requirements. But this also means they can track any user of these adblockers who has not disabled Acceptable Ads, even if they have installed privacy tools such as EasyPrivacy with the intention of protecting themselves. EFF is concerned about Criteo’s continued anti-privacy actions and their continued inclusion in Acceptable Ads.

    Safari Shuts out Third Party Cookies…

    All popular browsers give users control over who gets to set cookies, but Safari is the only one that blocks third-party cookies (those set by a domain other than the site you are visiting) by default. (Safari’s choice is important because only 5-10% of users ever change default settings in software.) Criteo relies on third-party cookies. Since users have little reason to visit Criteo’s own website, the company gets its cookies onto users’ machines through its integration on many online retail websites. Safari’s cookie blocking is a major problem for Criteo, especially given the large and lucrative nature of iPhone’s user base. Rather than accept this, Criteo has repeatedly implemented ways to defeat Safari’s privacy protections.

    One workaround researchers detected Criteo using was to redirect users from sites where their service was present to their own. For example, if you visited wintercoats.com and clicked on a product category, you would be first diverted to criteo.com and then redirected to wintercoats.com/down-filled. Although imperceptible to the user, this detour was enough to persuade the browser that criteo.com is a site you chose to visit, and therefore a first party entitled to set a cookie rather than a third party. Criteo applied for a patent on this method in August 2013.

    …And Closes the Backdoor

    Last summer, however, Apple unveiled a new version of Safari with more sophisticated cookie handling—called Intelligent Tracking Prevention (ITP)—which killed off the redirect technique as a means to circumvent the cookie controls. The browser now analyzes if the user has engaged with a website in a meaningful way before allowing it to set a cookie. The announcement triggered panic among advertising companies, whose trade association, the Interactive Advertising Bureau, denounced the feature and rushed out technical recommendations to work around it. Obviously the level of user “interaction” with Criteo during the redirect described above fails ITP’s test, which meant Criteo was locked out again.

    It appears that Criteo’s response was to abandon cookies for Safari users and to generate a persistent identifier by piggybacking on a key user safety technology called HSTS. When a browser connects to a site via HTTPS (i.e. a site that supports encryption), the site can respond with an HTTP Strict Transport Security policy (HSTS), instructing the browser to only contact it using HTTPS. Without a HSTS policy, your browser might try to connect to the site over regular old unencrypted HTTP in the future—and thus be vulnerable to a downgrade attack. Criteo used HSTS to sneak data into the browser cache to produce an identifier it could use to recognize the individual’s browser and profile them. This approach relied on the fact that it is difficult to clear HSTS data in Safari, requiring the user to purge the cache entirely to delete the identifier. For EFF, it is especially worrisome that Criteo used a technique that pits privacy protection against user security interests by targeting HSTS. Use of this mechanism was documented by Gotham City Research, an investment firm who have bet against Criteo’s stock.

    In early December, Apple released an update to iOS and Safari which disabled Criteo’s ability to exploit HSTS. This led to Criteo revising down their revenue forecasts and a sharp fall in their share price.

    How is Criteo Acceptable Advertising”****?

    "… w__e sort of seek the consent of users, just like we had done before_."__1_ - Erich Eichmann, CEO Criteo

    _"Only users who don’t already have a Criteo identifier will see the header or footer, and it is displayed only once per device. Thanks to [the?] Criteo advertisers network, most of your users would have already accepted our services on the website of another of our partner. On average, only 5% of your users will see the headers or footers, and for those who do, the typical opt-out rate is less than .2%._" - Criteo Support Center

    Criteo styles itself as a leader in privacy practices, yet they have dedicated significant engineering resources to circumventing privacy tools. They claim to have obtained user consent to tracking based on a minimal warning delivered in what we believe to be a highly confusing context. When a user first visits a site containing Criteo’s script, they received a small notice stating, _"_Click any link to use Criteo’s cross-site tracking technology." If the user continues to use the site, they are deemed to have consented. Little wonder that Criteo can boast of a low opt-out rate to their clients.

    Due to their observed behaviour prior to the ITP episode, Criteo’s incorporation into the Acceptable Ads in December 2015 aroused criticism among users of ad blockers. We have written elsewhere about how Acceptable Ads creates a clash of interests between adblocking companies and their users, especially those concerned with their privacy. But Criteo’s participation in Acceptable Ads brings into focus the substantive problem with the program itself. The criteria for Acceptable Ads are concerned chiefly with format and aesthetic aspects (e.g. How big is the ad? How visually intrusive? Does it blink?) and excludes privacy concerns. Retargeting is unpopular and mocked by users, in part because it wears its creepy tracking practices on its sleeve. Our view is that Criteo’s bad behavior should exclude its products from being deemed “acceptable” in any way.

    The fact that the Acceptable Ads Initiative has approved Criteo’s user-tracking-by-misusing-security-features ads is indicative of the privacy problems we believe to be at the heart of the Acceptable Ads program. In March this year, Eyeo announced an Acceptable Ads Committee that will control the criteria for Acceptable Ads in the future. The Committee should start by instituting a rule which excludes companies that circumvent explicit privacy tools or exploit user security technologies for the purpose of tracking.

    1. http://criteo.investorroom.com/download/Transcript_Q3+2017+Earnings_EDITED.pdf

    https://www.eff.org/deeplinks/2017/12/arms-race-against-trackers-safari-leads-criteo-30

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  • Have you ever sent a motivational text to a friend? If you have, perhaps you tailored your message to an activity or location by saying “Good luck in the race!” or “Have fun in New York!” Now, imagine doing this automatically with a compuuuter. What a great invention. Actually, no. That’s not a good invention, it’s our latest Stupid Patent of the Month.

    U.S. Patent No. 9,069,648 is titled “Systems and methods for delivering activity based suggestive (ABS) messages.” The patent describes sending “motivational messages,” based “on the current or anticipated activity of the user,” to a “personal electronic device.” The patent provides examples such as sending the message “don’t give up” when the user is running up a hill. The examples aren’t limited to health or exercise. For example, the patent suggests sending messages like “do not fear” and “God is with you” when a “user enters a dangerous neighborhood.”

    The patent’s description of its invention is filled with silly, non-standard acronyms like ABS for “activity based suggestive” messages or EBIF for “electronic based intelligence function.” These silly acronyms create an illusion of complexity where plain, descriptive language would reveal the mundane nature of the supposed invention. For example, what the patent grandly calls EBIF appears to be nothing more than standard computer processing.

    The ’648 patent is owned by Motivational Health Messaging LLC. While this may be a new company, at least one of the people behind it has been involved in massive patent trolling campaigns before. And the two named inventors have both been inventors on patents that trolls have asserted hundreds of times. One is also an inventor listed on patents asserted by infamous patent troll Shipping and Transit LLC. The other named inventor is the inventor on the patents asserted by Electronic Communication Technologies LLC. Those two entities (with their predecessors) brought over 700 lawsuits, many against very small businesses. In other words, the ’648 patent has been issued to Troll Co. at 1 Troll Street, Troll Town, Trollida USA.

    We believe that the claims of the ’648 patent are clearly invalid under the Supreme Court’s decision in Alice v. CLS Bank, which held abstract ideas do not become eligible for a patent merely because they are implemented in conventional computer technology. Indeed, the patent repeatedly emphasizes that the claimed methods are not tied to any particular hardware or software. For example, it states:

    The software and software logic described in this document … which comprises an ordered listing of executable instructions for implementing logical functions, can be embodied in any non-transitory computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions.

    The ’648 patent issued on June 30, 2015, a full year after the Supreme Court’s Alice ruling. Despite this, the patent examiner never even discussed the decision. If Alice is to mean anything at all, it has to be applied to an application like this one.

    In our view, if Motivational Health Messaging asserts its patent in court, any defendant that fought back should prevail under Alice. Indeed, we would hope that the court would strongly consider awarding attorney’s fees to the defendant in such a case. Shipping & Transit has now had two fee awards made against it for asserting patents that are clearly invalid under Alice. And the Federal Circuit recently held that fee awards can be appropriate when patent owners make objectively unreasonable argument concerning Alice.

    In addition to the problems under Alice, we believe the claims of the ’648 patent should have been rejected as obvious. When the application was filed in 2012, there was nothing new about sending motivational messages or automatically tailoring messages to things like location. In one proposed embodiment, the patent suggests that a “user walking to a hole may be delivered ABS messages, including reminders or instructions on how to play a particular hole.” But golf apps were already doing this. The Patent Office didn’t consider any real-world mobile phone applications when reviewing the application.

    If you want to look for prior art yourself, Unified Patents is running a crowdsourcing contest to find the best prior art to invalidate the ’648 patent. Aside from the warm feelings that come from fighting patent trolls, there is a $2000 prize pool.

    Despite the weakness of its patent, Motivational Health Messaging LLC might still send out demand letters. If you receive such a letter, you can contact EFF and we can help you find counsel.

    We have long complained that the Patent Office promotes patent trolling by granting obvious and/or abstract software patents. The history of the ’648 patent shows how the Patent Office’s failure to properly review applications leads to bad patents falling into the hands of trolls.

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