Tech firm tries to pull back curtain on surveillance efforts in Washington

Some specially outfitted smartphones are designed to act like high-tech divining rods that warn users of suspicious mobile activity, potentially indicating surveillance equipment used by police, intelligence agencies and others to track people and snoop on their calls.

Known as IMSI catchers, for the unique identifying phone code called an IMSI, the surveillance devices trick mobile phones into thinking they have logged onto legitimate cell networks, such as Verizon or AT&T, when in fact the signals have been hijacked. For years, researchers have warned of the growing prevalence of the equipment, and the spygear is rife throughout the Washington area, says Aaron Turner, chief executive of Integricell, a mobile security company.