Amazon Web Services gives developers access to massive computing capability. Now hackers have found ways to hijack some accounts and use that power to make money on someone else's dime.

Joe Moreno's bill for Amazon Web Services is usually about $5 a month. But last Thursday, he learned his AWS credentials had been compromised. An unknown person started renting computing power from Amazon on his account, racking up more than $5,300 in charges on servers in Amazon data centers as far away as Tokyo, São Paulo, Sydney, and Singapore.

It appeared that he was running processes that "mined" Bitcoin-creating units of the digital currency in exchange for processing transactions.

You might think this is an isolated case, but a security expert in Australia discovered almost 10,000 AWS credentials in a search of GitHub last month.

"I seem to be incapable of escaping my own stupidity," he said. But the unintentional publication of AWS credentials appears to be a common problem. It even happened to security researcher Rich Mogull in January.