Do you check your cell phone bill each month? If not, fake charges could be taking real money out of your wallet thanks to new malicious code being built into Android software.

In what's being called "toll fraud," malicious software embedded in some apps for Android smartphones is bringing back a new version of an old rip-off known as cramming.

The New York Times  reports that toll fraud puts phony charges through on your bill. The software secretly pings third party providers, pretending that you're asking to sign up for their pay services. Then crooks masquerade as you and secretly send back a confirmation that it was indeed you who initiated the sign up request.

A charge is confirmed to the cell phone operator by the crooks pretending to be you. Then the cell phone operator gets a cut of the action!

Apparently 18 million Android users are victims of toll fraud. The malicious code is so simple to implement that the number of those impacted will likely rise significantly from the 18 million mark. (Apple users are exempt from this.)

Unfortunately, most people don't review their cell phone bills. That's a big mistake. You need to go through your bill line item by line item and dispute any phony charges.

If you get stuck with a customer no-service representative on the phone while doing so, print out this show note. Send it to make the case that crooks could have created a fake acceptance for a billing charge, not you. And tell them you need that credit now!