How I bypassed the OTP verification process? Part — 1

Aditya Anand
Jul 1, 2018 · 3 min read

It’s been so long since I posted any article, partially because I was tired and taking a pleasant summer break. I was reading this particular article

After reading this I realised that I have had always tried different ways to try and bypass the login credentials but never those which had OTP verification process. So this article gave a me this feel that online profiles which have inbuilt OTP verification process is not super secure as well and from there onward I tried to carry out some attack on a website that uses OTP verification process.

Let’s dig in!

I started my attack on this website let’s say example.com, here I carried out my attack in two phase.

  1. Can I create a profile using a mobile no. that I don’t own? ( Identity theft )
  2. Can I get access to the account of a person, if all I know is their username or mobile number? ( How I bypassed the OTP verification process? Part — 2 )

The first hack

So to understand how to create a profile and how the system of OTP works on that particular website I went ahead and created my account. While I was doing that I took notice as to how the website worked?. Once done then I carried it out again for the another number that I own but this time the whole Idea was to create the account without having to touch my phone in anyway in which the sim was inserted.

So, here is how I began doing the hack. I inserted all the details as it should be. Now as I was done with it, I received an OTP on my phone instantly to verify and complete the process of a creating the account.

Burp Suite on!

I was presented with this and had to put in the OTP that I had just received on my mobile. I turned intercept mode on, and captured the packet which was being sent over as a request packet to the server.

The request packet I captured

So, I passed over the packet to the intruder tab to carry out a brute force attack and see if the website allowed multiple attempts for the OTP. Now, to figure it out I carried out a brute force attack, for the first attempt I saw the OTP that I got and made a long list of nearly 150 number and included it at the very end to just know if the process will work out or not.

Brute force attack

I guess I was in luck when the brute attack worked. Burp Suite was able to detect which one was the correct OTP.

Moral

This is one of the biggest mistakes that i have encountered in my time while carrying out pen-testing, where we never check the number of times the OTP is entered, or the number of times passwords are entered etc.

Prevention method for such brute force attacks could be a check that disallows any attempt made more than 3–5 times, or the OTP should not be valid further after 5 wrong attempts or so. This kind of security technique can be implemented and it will help curb a huge number of security issues.

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P.S. The attack where I was able to login into any user account will be discussed in another article, How I bypassed the OTP verification process? Part — 2.

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Aditya Anand

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CyberSec Professional | Hacker | Developer | Open Source Lover | Let’s connect - aditya12anand.com / patreon.com/aditya12anand

InfoSec Write-ups

A collection of write-ups from the best hackers in the world on topics ranging from bug bounties and CTFs to vulnhub machines, hardware challenges and real life encounters. In a nutshell, we are the largest InfoSec publication on Medium. #sharingiscaring