It was the largest bank robbery in history…

It started just hours after the U.S. invaded Iraq in 2003. Saddam Hussein and his sons looted over $1 billion in cash from the Central Bank of Iraq.

In 2005, Brazil's central bank was also robbed, this time in an Oceans 11-style heist. A gang of 35 bank robbers dug an 80-meter tunnel underneath a branch of the Central Bank of Brazil. They disguised themselves as landscapers to avoid detection while they constructed the tunnel. The gang made off with around $70 million in cash.

It's rare that any country's central bank is robbed. When it does happen, it's a huge story. It's not like knocking off the local liquor store or retail bank. Central banks are big game.

And it just happened again…

Last month, an international group of hackers robbed Bangladesh's account at the Federal Reserve, the central bank of the U.S.

First, the hackers used a computer virus to break into the security system of Bangladesh's central bank. Then they stole the usernames and passwords the bank uses for payment transfers. The hackers used this information to wire over $100 million from Bangladesh's Federal Reserve account to the Philippines and Sri Lanka. From there, they funneled it to casinos and withdrew it as cash.

The hackers cleverly executed the heist on a Friday. You see, Friday and Saturday are weekend days in Bangladesh. But Friday is a work day in the U.S. So, they were able to execute the bogus transfers without Bangladeshi government employees noticing for days.

Once Bangladesh realized what had happened, they couldn't stop it. By then, it was Sunday, and no one at the Fed was available to help. When they finally got in contact with the Fed, the $100 million had vanished. Bangladesh was left holding an empty bag.

Not surprisingly, the Bangladeshi government was furious. It lost confidence in the U.S.'s ability to safeguard the world's financial system.

Other countries likely have as well.