The goal of spoofing is to trick people into picking up the phone when their caller ID shows an innocuous name or number. Apparently, it's legal.

Ed Stoecker's brief, unintended and unhappy stint as a telemarketer occurred recently when he spent several days receiving angry calls from people who didn't appreciate his bothering them.

"They all saw my number on their caller ID screen," Stoecker, 58, told me. "They were upset that I seemed to have called them and then hung up just as they picked up the phone, like I was a robo-caller."

Needless to say, he wasn't the culprit. Stoecker was a victim of a growing problem called spoofing, a telephone sleight of hand that allows a scammer, telemarketer or debt collector to trick a caller ID system.

For example, instead of the name of a company or an 800 number, your caller ID screen might say "Customer Service" or show what looks like a non-commercial number.

The goal of spoofing is to fool people into picking up the phone, as well as to get around the federal government's Do Not Call list. It also can be used to dupe people into sharing personal information.

"The caller ID might say 'Los Angeles Police Department,' and the person at the other end of the line might ask for all sorts of information about you," said Robert Siciliano, an identity theft expert with security technology company McAfee.

"If you're not careful," he said, "you can get into real trouble."

And here's the real kick in the teeth: Spoofing isn't necessarily illegal.

The federal Truth in Caller ID Act makes it a crime to use a bogus phone number or caller ID message to commit fraud or cause harm to others, such as trying to con someone into giving out a Social Security number.

But it's not against the law to engage in what courts have called "non-harmful spoofing." The Fifth Circuit Court of Appeals last year said examples of non-harmful spoofing include a domestic-violence victim trying to hide her whereabouts or a consumer withholding his or her call-back number from a company.

But that loophole, no matter how well-intended, has been embraced by businesses as a way to "non-harmfully" get through a household's phone defenses.

"I bought a time share a few years ago," Siciliano said. "Now I get calls every day from people trying to sell me time shares, and they all use spoofing technology."

A Web search for "caller ID spoofing" will turn up numerous companies legally providing the service, such as SpoofCard, which offers 60 minutes of disguised calling for $9.95. "It's fun and affordable to spoof your friends," the company's website says.

The Federal Communications Commission declined to make anyone available to discuss regulation of spoofing. But a spokesman pointed me toward a 2011 agency report on the Truth in Caller ID Act.