The Washington, D.C., area is littered with devices that spy on users' cellphones, and one expert thinks they were planted by "a foreign entity," a new report says. The Washington Post reports that security experts using smartphones that can detect the presence of surveillance devices known as IMSI catchers found 18 of them during a recent drive through the region. Reporters from the Post tagged along on two consecutive days.The devices were detected near the White House, the Capitol, foreign embassies, and federal contractors near Dulles Airport.ESD America CEO Les Goldsmith, whose company builds a secure phone called the Cryptophone 500, told Venture Beat he believes the devices he and other security experts found in the nation's capital were not the work of the United States government."It's highly unlikely that federal law enforcement would be using mobile interceptors near the Senate," he said. "My suspicion is that it is a foreign entity."Several other news sources have written about IMSI catchers being found across the country. One story in Popular Science claims Goldsmith's firm discovered 17 of the spy devices in July nationwide. Coupled with more recent discoveries, the total number found across the country is now "about 45," Goldsmith told the Post.According to the Post, two types of interceptors were detected in Washington: One that captures a phone's information that can be used for monitoring at a later time, and one that has the ability to tap into phone calls.Goldsmith said the findings have been turned over to the Federal Communications Commission, which has expressed an interest in buying them.Earlier this month, CBS Chicago reported that interceptor towers had been discovered in Chicago. A former FBI agent told the station he didn't think law enforcement was behind their use."I doubt that they are installed by law enforcement as they require a warrant to intercept conversations or data and since the cell providers are ordered by the court to cooperate with the intercept, there really would be no need for this," Ross Rice said. "Most likely, they are installed and operated by hackers, trying to steal personal identification and passwords."Last month, it was announced that the FCC is looking into the use of IMSI catchers, which can also be referred to as stingrays, on U.S. soil. Law enforcement agencies have been using the devices in recent years, mostly to catch criminals.The use of these devices has generated a debate around privacy issues when it comes to law enforcement using them.Stephanie K. Pell of the Army Cyber Institute, meanwhile, told the Post last month that foreign governments could be listening to Americans' phone conversations through the devices."I think it would be prudent to assume that the Chinese government and criminal gangs don't care if IMSI catchers are illegal," Pell said. "Ultimately if we are going to get to the root of the problem, we will have to deal with this from a network vulnerability perspective."