Gone in six seconds: hackers only need seconds to guess card number and security code

It’s a terrifying thought that someone can gain access to our sensitive financial information in a short period of time and do with it what they will. And according to experts at Newcastle University, that period of time is extremely short indeed, six seconds in fact on Visa credit and debit cards.

In a study published in academic journal IEEE Security & Privacy, researchers found that it is “frighteningly easy” for an advanced criminal, using just a computer with an internet connection, to work out all the relevant information needed to make an online card payment.


‘Frighteningly easy’

The criminals use what is called a Distributed Guessing Attack to quickly work out card information. The computer automatically inputs numerous number variations of all the card data fields: card number, CVV code, expiry date etc on hundreds of websites. Within a matter of seconds, by simply eliminating what doesn’t work, the fraudster can have verified all those data fields.

This, says Mohammed Ali, a PhD student at the Newcastle University’s School of Computing Science, happens because the current online payment security systems do not detect multiple inputs of incorrect card information.

“Firstly, the current online payment system does not detect multiple invalid payment requests from different websites,” he said.

This allows an “unlimited” amount of guesses on each card data field. “This sort of attack exploits two weaknesses that on their own are not too severe but when used together, present a serious risk to the whole payment system,” he added.

He also said that different websites require different variations meaning that the fraudsters can essentially build up a clear card profile and assemble it together like pieces of a “jigsaw”.

When asked in an interview on Radio 4 whether he ultimately gets locked out of a website, Ali says that he does temporarily, but then he can just try another website.

It is thought that this Distributed Guessing Attack was the one used in the recent Tesco Bank fraud attack.


Visa responds

In response to the research, Visa has issued the following statement:

“The research does not take into account the multiple layers of fraud prevention that exist within the payments system, each of which must be met in order to make a transaction possible in the real world.

“Visa is committed to keeping fraud at low levels and works closely with card issuers and acquirers to make it very difficult to obtain and use cardholder data illegally.

“We provide issuers with the necessary data to make informed decisions on the risk of transactions. There are also steps that merchants and issuers can take to thwart brute force attempts.

“For consumers, the most important thing to remember is that if their card number is used fraudulently, the cardholder is protected from liability.”

The card company also mentioned its Verified by Visa, which introduced a 3D secure protocol, requiring online customers to enter a password that confirms the cardholder’s identity.

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