A hacker attack on SendGrid, an email service used by many companies including Coinbase, resulted in mass spam emails advertising Ponzi schemes being sent to users of Coinbase and Local Bitcoins.

On Wednesday evening, April 8th, the bitcoin community started to receive spam letters from the address This email address is being protected from spambots. You need JavaScript enabled to view it.. The text announced the launch of a “Coinbase Invest Fund”, “insured by institutions such as the New York Stock Exchange”. It guaranteed a 150% return for any deposit up to 60 bitcoins payable on May 1st. For deposits exceeding 30 bitcoins, “a 2nd level upgrade” to membership was promised. The text ended with the exhortation to “Hurry up! This is a limited, one-time opportunity”. The letter also included a bitcoin address for the deposit. According to Reddit users, different people received different addresses for the payment.

Redditors were ironic about the promises of the letter. One of them wrote:

“The Nigerian prince will be sending me money any day now. I’ll be sure to invest. Thanks.”

After an investigation, Coinbase discovered that the letters were sent because email account associated with the email service SendGrid were compromised. However, Coinbase declared that as SendGrid was used only as a backup email provider, no Coinbase customer data was affected. SendGrid believes it was just an isolated attack.

This is not the first time that hackers target Coinbase. Phishing letters from its accounts were sent in November 2014 and February 2015. According to the Qntra.net website, “Customers of this service make for especially good targets seeing as how they are the kind of people who prefer user friendliness over actual security”. However, the hackers probably just targeted a popular company with many customers. As CoinFox wrote, Coinbase is reportedly the second most popular wallet service.

In March, hackers also sent phishing letters to BitStamp customers.

According to a recent study, during the last four years bitcoin users have lost $11 million to bitcoin scammers. Out of this sum, $7.3 million were lost to high-yield investment scams also known as Ponzi schemes.