Add tip for SMS based 2FA usage

README.md

@@ -53,7 +53,7 @@ Use long, strong and unique passwords, manage them in a secure password manager,
 **Avoid password hints** | Optional | Some sites allow you to set password hints. Often it is very easy to guess answers. In cases where password hints are mandatory use random answers and record them in password manager (`Name of the first school: 6D-02-8B-!a-E8-8F-81`)
 **Never answer online security questions truthfully** | Optional | If a site asks  security questions (such as place of birth, mother's maiden name or first car etc), don't provide real answers. It is a trivial task for hackers to find out this information online or through social engineering. Instead, create a fictitious answer, and store it inside your password manager. Using real-words is better than random characters, [explained here](https://news.ycombinator.com/item?id=29244870)
 **Don’t use a 4-digit PIN** | Optional | Don’t use a short PIN to access your smartphone or computer. Instead, use a text password or much longer pin. Numeric passphrases are easy crack, (A 4-digit pin has 10,000 combinations, compared to 7.4 million for a 4-character alpha-numeric code)
-**Avoid using SMS for 2FA** | Optional | When enabling multi-factor authentication, opt for app-based codes or a hardware token, if supported. SMS is susceptible to a number of common threats, such as [SIM-swapping](https://www.maketecheasier.com/sim-card-hijacking) and [interception](https://secure-voice.com/ss7_attacks). There's also no guarantee of how securely your phone number will be stored, or what else it will be used for. From a practical point of view, SMS will only work when you have signal, and can be slow
+**Avoid using SMS for 2FA** | Optional | When enabling multi-factor authentication, opt for app-based codes or a hardware token, if supported. SMS is susceptible to a number of common threats, such as [SIM-swapping](https://www.maketecheasier.com/sim-card-hijacking) and [interception](https://secure-voice.com/ss7_attacks). There's also no guarantee of how securely your phone number will be stored, or what else it will be used for. From a practical point of view, SMS will only work when you have signal, and can be slow. If a website or service requires the usage of a SMS number for recovery consider purchasing a second pre-paid phone number only used for account recovery for these instances.
 **Avoid using your PM to Generate OTPs** | Advanced | Many password managers are also able to generate 2FA codes. It is best not to use your primary password manager as your 2FA authenticator as well, since it would become a single point of failure if compromised. Instead use a dedicated [authenticator app](/5_Privacy_Respecting_Software.md#2-factor-authentication) on your phone or laptop
 **Avoid Face Unlock** | Advanced | Most phones and laptops offer a facial recognition authentication feature, using the camera to compare a snapshot of your face with a stored hash. It may be very convenient, but there are numerous ways to [fool it](https://www.forbes.com/sites/jvchamary/2017/09/18/security-apple-face-id-iphone-x/) and gain access to the device, through digital photos and reconstructions from CCTV footage. Unlike your password- there are likely photos of your face on the internet, and videos recorded by surveillance cameras
 **Watch out for Keyloggers** | Advanced | A hardware [keylogger](https://en.wikipedia.org/wiki/Hardware_keylogger) is a physical device planted between your keyboard and the USB port, which intercepts all key strokes, and sometimes relays data to a remote server. It gives a hacker access to everything typed, including passwords. The best way to stay protected, is just by checking your USB connection after your PC has been unattended. It is also possible for keyloggers to be planted inside the keyboard housing, so look for any signs that the case has been tampered with, and consider bringing your own keyboard to work. Data typed on a virtual keyboard, pasted from the clipboard or auto-filled by a password manager can not be intercepted by a hardware keylogger, so if you are on a public computer, consider typing passwords with the on-screen keyboard