SMS codes were long considered a simple and reliable way to protect accounts. Banks, social networks, and online services widely used SMS as a second authentication factor. However, by 2026 it has become clear: SMS codes no longer provide real security and in many cases only create an illusion of protection.
Why SMS was considered secure
The idea behind SMS authentication was based on a few assumptions:
- The phone is always with its owner.
- The phone number is difficult to intercept remotely.
- One-time codes are valid for a limited time.
In practice, all of these assumptions no longer reflect reality.
SIM swap — the main threat to SMS authentication
SIM swap is one of the most common attack methods in recent years.
An attacker:
- Obtains the victim’s personal data.
- Contacts the mobile carrier.
- Reissues the SIM card in their own name.
After that, all SMS messages — including verification codes — are delivered directly to the attacker.
Why SIM swap works
- Mobile carriers often rely on weak identity verification.
- Human error in customer support.
- Personal data breaches make attacks easier.
As a result, the attacker gains full control over the victim’s accounts.
Vulnerabilities in mobile infrastructure (SS7)
Mobile networks rely on legacy signaling protocols such as SS7, which were not designed with modern security threats in mind.
This allows attackers to:
- Intercept SMS messages without access to the phone.
- Track a subscriber’s location.
- Manipulate message delivery.
Access to such attacks is no longer limited to governments — it is also available to commercial entities and cybercriminals.
SMS interception via malicious applications
On smartphones, SMS messages can be compromised through applications:
- Malware and spyware.
- Apps with excessive permissions.
- SDKs that have access to messages.
Android devices are especially vulnerable, as users often grant SMS permissions without fully understanding the consequences.
Social engineering and phishing
SMS codes are frequently exploited in social engineering attacks:
- Users are tricked into revealing the code.
- The code is entered on a phishing website.
- The attack happens in real time.
The one-time nature of the code does not help if the user gives it to the attacker themselves.
Dependence on phone numbers
Phone numbers are no longer a reliable identifier:
- Numbers are sold and resold.
- Carriers reuse old numbers.
- Phones can be lost or temporarily disconnected.
At the same time, many services tightly bind account access to a phone number, increasing the risk of lockouts or account takeover.
Why banks and services still use SMS
Despite the risks, SMS remains popular because:
- Users are familiar with it.
- No additional apps are required.
- It works on any phone.
This is a trade-off between convenience and security — and security loses.
What should replace SMS codes
More reliable alternatives include:
- Authenticator apps (TOTP).
- Hardware security keys (U2F / FIDO2).
- Push-based authentication with cryptographic signatures.
- Passkeys and passwordless login.
These methods do not depend on mobile carriers and are significantly harder to attack.
When SMS may still be acceptable
SMS can only be used as:
- A temporary solution.
- A backup recovery method.
But not as the primary protection mechanism for critical accounts.
Conclusion
In 2026, SMS codes are an outdated technology that does not match modern threat models. SIM swap attacks, mobile network vulnerabilities, malicious applications, and social engineering make SMS an unreliable authentication method.
Using SMS for authentication is not about convenience — it is about risk. To protect accounts, finances, and personal data, it is essential to move to modern, cryptographically secure authentication methods.