Cash means crime. It's as attractive to street thugs as it is to Bond villains. You can spend it anywhere, on anything, and it's almost completely anonymous.

Scientists have long suspected that reducing the role of cash in American society might reduce the incidence of physical crime. As my colleague Chris Ingraham notes, a new economic study shows switching people from paper welfare checks to electronic debit cards is linked to a drop in assaults, burglaries and robberies.

The findings suggest a cashless society would indeed be a more peaceful one. But even as fewer people use cash for everyday transactions, that creates opportunities for new kinds of theft that involve very different players, wielding a very different playbook.

The question now isn't whether electronic payment methods reduce crime. It's whether they're changing the criminal landscape in a way that reduces some crimes and facilitates others.

Instead of assault and burglary, we're seeing a rise in malware and botnets. Rather than beefy bullies who commit crimes of opportunity, skilled hackers are increasingly probing corporations for gaps in security. A robust industry has grown up around the sale of digital exploits. And the more we move away from cash, the more vulnerable to these attacks we become.

"No one knows (or is willing to hazard a guess) how many people participate in" online crime, according to a report this week by the RAND Corporation. "Similarly, few want to estimate how large the market is, although the general feeling is that it is large, and one expert noted that it generates billions of dollars, at the least."

Contributing to this digital manifestation of the physical black market are alternatives to traditional money altogether. Officials fearful of its cash-like characteristics have singled out Bitcoin as a potential threat. Some have even called for a ban on the virtual currency, saying it enables the illegal online trade in drugs and weapons.

Bitcoin defenders say this is really no different from the way cash works. The comparison may be more apt than they realize. Bitcoins can go missing. According to Mt. Gox, which lost hundreds of thousands of bitcoins, they can be hacked and stolen if the right precautions haven't been put in place.

Not everyone is an avid user of Bitcoin — yet. But you don't have to understand how we're increasingly dealing with money as numbers on a screen instead of greenbacks in a wallet. And that's creating a new industry in crime, even if our streets are getting safer because of it.