Four ways to smuggle messages through internet services

Their neighbors thought they were just ordinary U.S. residents, but secretly they were spies, sent by Russia's Foreign Intelligence Service to gather information on U.S. policies and programs. For years they thwarted detection, partly by hiding secret correspondence in seemingly innocent pictures posted on public websites. They encoded and decoded the dispatches using custommade software. But the scheme wasn't as covert as the spies had assumed. Eventually, investigators from the U.S. Department of Justice tracked down the altered images, which helped build a case against the Russians. In June 2010, federal agents arrested 10 of them, who admitted to being secret agents a few weeks later.