"Playing hooky without getting caught — as immortalized in the cat-and-mouse skirmish between Ferris Bueller and Principal Rooney in Ferris Bueller's Day Off — used to be an adolescent rite of passage," says Eric Spitznagel in Bloomberg BusinessWeek. Now it's a growing industry: As workers increasingly fake sick days, companies are hiring private detectives and off-duty cops to catch them. Here are some key takeaways from Spitznagel's article:

Employers are gunning for you, perhaps with reason
The number of workers who have falsely called in sick has jumped almost 20 percent since 2008, according to workforce productivity company Kronos, and now 57 percent of U.S. salaried workers play hooky. Employers have noticed, and more and more are trying to catch workers in the act. Detective agencies are reaping the benefits. It "can sometimes require multiple days, or even weeks," to catch a cheating worker, says Mario Pecoraro Jr., whose Alliance Worldwide Investigative Group charges $75 an hour.

Federal courts are letting bosses snoop
A watershed moment for the "new and expanding niche" of sick-day detectives was the case of Diana Vail vs. her employer, Raybestos Products. Raybestos fired Vail after an off-duty cop they'd hired showed that she was abusing her paid sick leave. Vail sued, but the 7th U.S. Circuit Court of Appeals dismissed her lawsuit, saying that spying on workers "may not be preferred employer behavior," but it isn't illegal. Many companies took that as a green light to snoop.

10 percent unemployment is making people "sick"
Risking your job by lying about being sick may not make sense during a job crisis, but the high unemployment rate is actually contributing to the rise in truancy, says Kronos Senior Director Joyce Maroney. "People are staying in jobs they don't like because of a fear that there won't be another job out there," she says. And when workers aren't happy in their jobs, "there's a greater propensity for sick-time abuse."

Predictably, there's a how-to-cheat industry
Detectives are playing both sides of the field. Equal-opportunity "privacy consultants" like New York-based Frank Ahearn offer their services to both companies and employees trying to avoid getting caught: "If you understand how to use technology effectively, you can appear to be anywhere." Aheran tells of an employer who gave his workers GPS phones so he could track them, including one employee who sent his phone on a business trip via FedEx while he enjoyed an exotic vacation.

"Whoever has the best technology usually wins"
So says Ahearn, and there's a whole industry to back up his words. "One popular toy among the adult Ferris Bueller set is the SpoofCard," says Spitznagel. The card, sold by TelTech Systems, lets you make it look like your call is coming from whatever 10-digit phone number you chose — for example, your home phone number, when you're in Barbados. Of course TelTech also sells the LiarCard, which uses voice analysis to let HR offices and others know if the caller is being dishonest.

Read the full article at Bloomberg BusinessWeek.