With so much sensitive information streaming through the Internet, it's no wonder that high-tech crime-fighting units are springing up all over the country to combat digital fraud, theft, and sabotage.

Police sergeant Don Brister of the High Technology Crimes Detail in San Jose, Calif., investigates corporate espionage, among other offenses. Brister warns that with such crimes on the rise, companies should do more than build firewalls to protect their inner systems. They should also keep a sharp eye on what's going on within the organization. Follow these few simple precautions, Brister says, and protect your company from digital mischief.

Since most corporate computer crimes are committed by former and current employees, Brister suggests that companies sever their ties with bad employees immediately. Allowing a recently fired staffer to stick around for the standard two weeks allows that worker to gather all the information and security codes necessary for future hacking. "That's the making of a disgruntled employee who can do a lot of damage," Brister says. "Almost any employee can bring a business to its knees. Managers and owners should look at immediate dismissal as protecting the business early on, even if it means losing a few dollars by not having a person there."

Companies can prevent a lot of trouble, Brister says, if they conduct complete background checks on prospective hires. "We've been involved in many cases in which warehouse people, even people in the financial department, have had criminal records," he says. "Even though that history is public, the company hasn't known that it's available or how important it is. And while many organizations would rather be kindhearted than suspicious, there are people who will go from company to company and continue stealing."

Brister says it's important to call in the law at the first sign of trouble. Don't wait until a series of crimes have occurred. Early reporting means that police can log the incidents and have more leads to follow. Even if there isn't yet a high-tech-crime unit in your city, Brister says, state police departments often have forensic computer labs. And if state agencies aren't able to help, Brister suggests calling the FBI, the Secret Service, the U.S. Customs Service, or even the post office.