To Spy on a Cheating Spouse: USE SOFTWARE, NOT GADGETS.

• Author: McCullagh, Declan

IN THE UNFORTUNATE event that your marriage does not last, it may at least end amicably. Or it may not, in which case its final days might need to be accompanied by the kind of aggressive electronic surveillance that once was used only by three-letter federal agencies.

But be warned if you're thinking about snooping on your spouse: A little-known section of federal law enacted in 1968, 18 USC 2512, makes it a crime to manufacture, assemble, or even possess any "device" that is "primarily useful for the purpose of the surreptitious interception of wire, oral, or electronic communications."

Section 2512 goes beyond merely regulating whether any such device is used for good or ill. Instead, it's a far-ranging prohibition on everything, up to and including advertising, an eavesdropping device, based on the premise that unlawful wiretapping will be less prevalent if the tools are less available. Service providers like AT&T and Comcast are exempt. So, of course, are police, other government agencies, and their contractors.

The legislative history from the 1960s reveals that Congress wanted to ban products such as microphones disguised as wristwatches, as well as so-called infinity transmitters that send audio from a room over a phone line, giving the snooper an effectively infinite listening range. The danger of a "martini olive transmitter" was also cited, perhaps by legislative staffers who took the early James Bond movies a little too seriously. In the 1990s, federal prosecutors successfully invoked this law against The Spy Factory, which operated 16 retail stores that sold bugging and wiretapping equipment to the general public.

But thanks to Section 2512 's practically antediluvian origins dating to the era of mainframes and punched cards, a loophole has been growing wider every year. That's because the pre-ARPANET statute only bans eavesdropping hardware. Congress revisited the law in 1986 as part of the Electronic Communications Privacy Act but ended up leaving Section 2512 intact.

If someone sells a laptop, phone, or home assistant with preinstalled software that spies on the user without his or her knowledge, that likely violates Section 2512 since those are surely all "devices." Computer code is more slippery. One federal district court in Ohio concluded in 2008 that "software alone... does not fit into this definition."

In our increasingly networked world, this oversight offers a remarkable escape clause--and a useful reminder of the...