April 21, 2024

Out-of-Band Authentication: Moving Beyond Traditional Password-based Logins

With cybersecurity threats rising at an alarming rate, account takeovers are becoming increasingly common. Hackers are ramping up attempts to gain unauthorized access to user accounts by stealing passwords through phishing scams and malware infections. However, login credentials alone are no longer enough to securely authenticate users. Out-of-band authentication provides an extra layer of protection by verifying users through a separate channel.

What is Out-of-Band Authentication?
Out-of-band authentication refers to confirming a user’s identity using a communication channel different than the one used for the primary login attempt. Instead of relying solely on passwords, it leverages an additional verifiable factor such as a registered phone number or email address. For example, when a user tries signing in on a website, the service sends a one-time passcode to their mobile device. Only by entering this code on the website can they complete the authentication process.

Two-Factor Authentication vs Out-of-Band
Two-factor authentication adds a second factor like a security token or biometric alongside the password. However, both factors are still entered on the same device or platform. Out-of-band authentication differs in that the secondary verification step occurs on a separate channel, making it harder for attackers to intercept login credentials as well as confirmation details in a single breach.

Implementation in Popular Services
Major technology companies like Google, Microsoft and Facebook have incorporated out-of-band authentication into their sign-in workflows. Some implementations include:

– Google prompts for a verification code to be entered when signing in from an unrecognized device or browser. It sends these codes to the user’s registered mobile number via SMS or phone call.

– Microsoft Azure Active Directory allows administrators to configure authentication apps for generating one-time passcodes. When users sign in, they must provide the code from the separate mobile app in addition to their password.

– For high-risk Facebook logins, an authentication code is sent via SMS, phone call or email depending on the contact methods linked to the account. Login is blocked until the correct code is supplied.

– PayPal sends out transaction confirmation codes to verified mobile numbers and emails. Customers must provide these codes to complete high-value payments from their accounts for added security.

Challenges of Implementing Out-of-Band Authentication
While offering stronger protection against unauthorized access, out-of-band authentication also poses some implementation challenges for organizations:

Contact Information Management
Reliance on phone numbers and emails for verification assumes these contact details are always up to date for each user. However, people do change numbers and addresses frequently. Services need robust processes for users to update their information promptly.

Consumer Adoption
The extra step of confirmation through a separate channel could create friction in the login workflow and discourage some users. Services must design intuitive and streamlined processes to boost adoption without compromising security.

Access Issues
There is a risk of customers getting locked out of their accounts if their registered mobile devices are inaccessible at the time of login. Services need fallback options like alternative identifiers and support channels to help users in such situations.

Multi-Device Sign-ins
Supporting authentication across a range of devices from desktop to native apps becomes more complex. Creative solutions are needed for verifying users seamlessly regardless of platform.

Privacy Concerns
Storing phone numbers and personal identifiers as second factors could raise privacy red flags for some. Transparency around data collection and usage is important to address such concerns.

Future of Out-of-Band Authentication
As threats to online user accounts persist, out-of-band authentication will play a more dominant role in the future. Beyond passwords, it establishes another verifiable layer tied to a user’s real identity. Technologies like push notifications and biometric authentication on mobile devices also open up new possibilities. Standards like FIDO are striving to enable simpler and more secure sign-ins across platforms using such second factors accessed outside the web. With stronger adoption and innovation to overcome current challenges, out-of-band authentication certainly holds promise to reshape online identity verification.


  1. Source: Coherent Market Insights, Public sources, Desk research
  2. We have leveraged AI tools to mine information and compile it