Sitting down with your checkbook to pay bills can be one of the riskiest things you do every month. If the wrong person gets their hands on that string of numbers running across the bottom of your check, you could be in trouble.

“I just knew that couldn't be possible,” a woman named Gretchen told KGW.

Gretchen says she's diligent about calling her bank, and this time it paid off when she spotted a check that didn't make sense.

“Once I found out it was a fraudulent check, I felt like our privacy had really been invaded,” says Gretchen.

Gretchen's husband John has a banking background. They fear identity thieves might target them, so KGW agreed not to disclose their full names.

“Imagine if you had not looked at your account for weeks or months or over a period of a quarter,” says John. “I’m not sure the banks would even cover some of your losses.”

The phony check had a name and address that were made up, but the account and routing numbers were Gretchen's.

It appears that a crook simply stole that information, then used a common software program anyone could buy to create and print checks.

Local fraud investigators say this type of check fraud is running rampant. According to the secret service, more than 175,000 phony checks are presented every day in our country. It adds up to $5 billion in losses a year.

“I think maybe the banks need to come up with a different check system, a different numbering system on your check,” says John.

While banks have yet to encode or protect your account numbers on physical checks, you can get added protection by taking advantage of new on-line checking accounts that pay your bills for you.

“We take the money out of your account and we generate a check, “ says Sung Hung Ho with Washington Mutual Bank, “and then send it to the merchant you are paying so your account information is never exposed.”

With bill pay, no one ever gets to see your checking or routing numbers.

“You need to protect all your account information like it was worth all the gold in Fort Knox,” says Tom Unger with Wells Fargo Bank.

When KGW asked Gretchen if her experience changed the way she felt about using checks, she responded: “Yes, I think we'll be paying more things on line.”

Banking on line truly may be your best protection. But if you're still more comfortable writing checks, or don't have Internet access, there are ways to protect yourself.

Don't use your mailbox to send out checks. Take them to a secure box or post office. ID thieves constantly steal mail - that includes those canceled checks that come in the mail each month. You can simply ask your bank to stop sending those canceled checks. Don't worry if you need one for your records. You can still get it simply by calling your bank.

MORE: American Bankers Association

ALSO: Secret Service