If a race of advanced beings wanted to wipe out Earths digital monetary system, how might they go about doing so? Answers from real science and speculative science (pseudo-science) are fine.
Most digital currency relies on some form of encryption. If the advanced beings possess the computational power to break the encryption they could manipulate the system in many ways, transfering all wealth into their own account, all properly validated.
An interesting story idea, the invading aliens would, according to our own records, own all the Earth's assets.
"a race of advanced beings" <- you have your answer.
A super computer virus which utterly crushes the software security of those pathetic human worms.
Most major systems are connected to the internet in some way, so the virus can insinuate itself into their networks easily.
For better protected systems which are being housed in bunkers with no connection to the internet (i'm assuming such setups exist) your super-virus is going to have to get a little more creative, but I'm assuming it won't be a problem, or that what a virus can't wreck a well-aimed rock dropped from orbit will.
Do it Project Mayhem Style
In the popular movie Fight Club the narrator meets a man named Tyler Durden and a series of events leads them to become friends and start a club wherepeople fight.
What does this have to do with your scenario? Well, one of Tylers plans is to start project mayhem which involves using explosive soap to blow up buildings. What buildings? The building of the credit card companies, which in turn destroys their servers and information storage, resetting the debt systems