The Mastercard system, which allows customers to send money to each other and pay merchants on their behalf, is widely considered the most secure form of payment in the world.
The company’s CEO, John P. Donahoe, has said that he believed it was safe.
But that belief has been questioned.
Last year, a hacker called Coin Master exploited the company’s Mastercard website to steal nearly $40 million.
The attacker exploited vulnerabilities in the Mastercard database.
Now, the hackers behind Coin Master have released the details of their attack, which they say is the largest yet against the Master card network.
It has been called one of the largest security breaches in history, but the hacker behind it is anonymous and says it did not steal money.
Coin Master said it took the threat seriously and that it took steps to protect itself.
Coin Masters claims it is the world’s largest maker of credit card processors, but it does not specify how many customers have used the system to send payments.
CoinMaster, a Philadelphia-based payment processing company that has offices in New York and San Francisco, was founded in 2005 by three former Wall Street executives.
It’s the only U.S. company that uses the Visa system, and the company said it is not connected to the MasterCard system.
It said it has about 300,000 active credit card accounts worldwide and that about 5 percent of them have been compromised.
Coin Maker has not provided details about the number of customers who have used it.
CoinMasters founder and CEO Jonathan Shuster said his company uses an algorithm that uses public information about customers to find which cards they have.
That information is publicly available on Coin Maker’s website.
CoinMaker says it will be able to verify customers’ identity and the identity of the card issuer by using their credit card numbers.
Shuster added that Coin Maker uses the information from the card to determine if customers want to send or receive a payment.
Coinmaker says it doesn’t store any information about how customers spend their money.
The hack has drawn widespread attention from cybersecurity experts and government agencies.
Federal investigators are examining CoinMaker’s security.
The Federal Bureau of Investigation is looking into CoinMaker and the breach, the U.K.’s Financial Conduct Authority is investigating and the New York State Attorney General is investigating.
In a statement released Monday, Coin Maker said it was working with federal authorities and the FBI.
It noted that it will take time to fully investigate the breach.
Shustner said Coin Maker does not store any data about customers.
Shuretner added that the company will take steps to safeguard customers’ information.
Coin maker says its security measures were “well-secured” CoinMaker said it also took measures to protect customer data and security, including using a combination of password hashing and hashing algorithms to prevent the hackers from gaining access to the company.
Shutetner said that while the company had never received a single fraudulent credit card, CoinMaker had experienced “an increase in card fraud activity over the past few years, which has caused us to review our security protocols to prevent fraud in the future.”
Coin Maker also said that it would work with the Department of Homeland Security to help identify the hackers.
The FBI is investigating Coin Maker and said Monday it is looking at Coin Maker for possible fraud.
The department said it had received reports that at least one of Coin Maker employees had worked at Visa since the beginning of 2014.
The bureau said it would conduct a review of the breach and take further action if appropriate.
Coin makers spokeswoman Kristina E. Osterman said the company has a number of measures in place to protect customers’ data.
Coinmakers security team has a list of all customers who use CoinMaker, including their names, addresses, card numbers and other personal information, she said.
Coin’s website said CoinMaker was not compromised in any way.
Coin is a pioneer in the payment processing industry and one of a handful of companies that uses a digital currency.
Its platform allows users to send and receive money from a mobile device, and it says it processes more than $50 billion worth of transactions a day on behalf of merchants.
Coin said it will continue to invest in its network.
The credit card network is also among the most popular in the United States, and Coin has more than 7 million cards in circulation, according to the U-M Visa Card MasterCard database.
Coin has been the target of several other hacks over the years.
Coin hackers broke into Visa’s systems in 2009 and 2010.
In 2011, a group of hackers broke through the Master Card network and stole about $10 million worth of data.
The hacker who broke into the Master Visa system in 2009 is also known as the BlackHole Project.
The group that broke into Master Visa in 2010 also stole credit card data.