Money muling is a phishing scam growing in popularity.

In the illegal drug trade, couriers used to transport contraband are called mules. But in the phishing world, the term takes on a whole new meaning.

The vehicles that phishers use to recruit unwitting mules are familiar fare. They include job postings, mystery shopping and online surveys. Once a phish takes the bait, the bunco artist persuades the target to cough up some money in exchange for the promise of greater rewards. Often the mark receives a check, is instructed to deposit it into a personal bank account and to return a portion of the money to the phisher via wire transfer or certified check.

In the employment version of the scam, a job seeker receives an e-mail solicitation from a company in a foreign country stating it’s looking for people to process their payments. Why it needs its payments processed by individuals is usually sketchy, but avoiding taxes is a typical dodge. All the job seeker needs to do is deposit a check–usually ranging from $200 to $2000– from the company into his or her bank account, subtract 10 percent from the total deposit and wire the rest of the money to the phony firm.

What makes the scheme particularly insidious is that banks often become an unintentional co-conspirator of the phisher. A wary target suspicious of easy money pitches may decide to deposit the phisher’s check, but wait until the bank says that the paper has cleared. When the phish receives that approval, he or she happily complies with the bogus business’s wishes, confident that the transaction is legitimate.

Moreover, because the phishers filch such small amounts from their victims, they can stay off the radar of law enforcement agencies, who are usually looking for bigger phish to fry. Oftentimes, muling victims looking for relief from national law enforement agencies feel that submitting a complaint to one of those agencies is like tossing a paper plane into a black hole.

Although city and town police departments may be more interested in pursuing online scammers in their jurisdictions, they’re unable to track down and cage international criminals like those perpetrating muling cons.

What the target doesn’t know is that banks “clear” checks before they know that the money to cover the check is actually in the account on which the check is written or even if the account exists in the first place. Banks will typically release the funds for a check five to 10 days  after it’s deposited, yet may not really know if the funds exist for 15 to 21 days after they get their hands on it.

What’s more, a person who deposited the check is responsible for it–whether the bank makes a mistake in clearing it or not–so he or she must make good on the check. The mule ends up paying for the check twice–once to the phishers and once to the bank.

To make matters worse, as part of the application process for participating in the payment program, phishers will try to gather enough personal information about a mule to steal their identity. If they can’t get a mark’s money, they still hope to profit by selling his or her identity on the black market.

Up to now, phishers have focused their muling swindles, for the most part, on the English-speaking world, with the exception of Spain–Canada, United States, United Kingdom, Australia and New Zealand. The scam appears to be popular with fraudsters in Poland, Germany, Russia and China.

Popular targets for muling include the housewife, the retiree, the college grad and the displaced worker, but since e-mail is a key tool in the info-bandit’s repertoire, corporate mail systems can be impacted by the scam, too.

Although about 70 percent of muling scams are perpetrated through e-mail, phishers have also used classified sites like Craigslist and job aggregators like CareerBuilder.com to snare victims. Sometimes the scammers pose as legitimate businesses to obtain lists of job searchers from employment sites so they can add credibility to their e-mail solicitations. If they know a target has submitted a resume to a CareerBuilder.com, they can reference that site in their pitch and appear to be an authentic employer.

Thus far, money muling has been a con for small time cyberthieves, but the ability of its practitioners to run their scams with impunity is sure to attract the notice of more organized criminal elements who know a good thing when they see it.