How to Protect Your Phone Number Online

Your phone number is more than a way to call you. It is a login identifier, a password-reset channel and a link between your accounts. When it leaks, you get spam calls, phishing SMS and, in the worst case, account takeovers.

Why your number is valuable to attackers

• It connects accounts across services, so it is used to build profiles.
• Many services still allow password reset by SMS.
• A SIM-swap attack gives the attacker every code sent to your number.

Share your real number only where it matters

Keep your personal number for your bank, government services, your main email and close contacts. For marketplaces, one-time sign-ups, giveaways, Wi-Fi portals and apps you are only trying out, use a temporary virtual number.

Switch SMS codes to an authenticator app

Wherever possible, replace SMS two-factor authentication with an authenticator app (Google Authenticator, Authy, 1Password) or a security key. App codes cannot be intercepted with a SIM swap.

Lock your SIM at the operator

• Set a SIM PIN on your phone.
• Ask your operator for a port-out / SIM change PIN or extra verification.
• Be suspicious if your phone suddenly loses signal: call your operator right away.

Hide your number in apps

• Telegram, WhatsApp: set phone number visibility to "Nobody" or "My contacts".
• Social networks: remove the number from your public profile and turn off "find me by phone number".
• Contact sync: only allow apps you trust to read your contacts.

Watch for phishing SMS

Banks and delivery companies never ask for your verification code. If a message asks you to "confirm" a code or click a link to avoid a fee, delete it.

Check whether your number leaked

Breach notification services let you check whether your number or email appears in known data leaks. If it does, change passwords on those services and enable app-based 2FA.

Rule of thumb: if you would not give a stranger your number, do not give it to a website you just found either.