Who's at the back door?

Everyone knows you should always make sure that the backdoor to your house is locked. But in computer networks, it's not always easy to tell if someone has built a new backdoor, one you don't know about.

Jay Valentine, head of Infoglide, a firm that invented a software program that can track how criminals or terrorists change identities online, says there are tens of thousands of "backdoors" in government computers. He explains a backdoor as being "an entry point which is found or created through someone's [security system] fire wall. The major US government institutions all have fire walls. These prevent unauthorized access. But people get through all the time. Sometimes they are detected and the fire wall is adjusted.

"Many people, however, constantly attack these fire walls and do get through, undetected," Mr. Valentine says. "When they get through, rather than cause a problem and thus get detected, they simply create a program which enables them to re-create the entry. This is the backdoor."

How do they get through the fire wall in the first place? Some enter via access in the fire wall granted to a vendor, or find holes in the fire wall that have been created so that department heads or a company director can check an office computer for e-mail or other files. Some hackers use machines that constantly dial phone numbers, looking for a modem line that will lead them into a computer network. Others just find holes left because of lax security.

Many government organizations or companies may never know security has been breached until it's too late, says Valentine.