anitrd 0%tatra 0%mw WASHINGTON DC 20510 April 18 2018 Christopher C Krebs Senior Of cial Performing the Duties of the Under Secretary National Protection and Program Directorate Department of Homeland Security Washington DC 20528 Dear Mr Krebs We write to urge the Department of Homeland Security publish additional information about incidents in which cellular surveillance devices have been detected in the National Capital Region In a March 26 2018 letter to Senator Wyden you revealed that DHS has observed anomalous activity in the National Capital Region N CR that appears to be consistent with International Mobile Subscriber Identity IMSI catchers NPPD has not validated or attributed such activity to speci c entities or devices DHS has in recent months shared additional information about these and other incidents with federal agencies Speci cally an of cial from the DHS National Coordinating Center for Communications N CC gave a detailed presentation on Mobile Threats at the Federal Mobile Technology Forum in Mclean VA on February 6 2018 While informative the unclassi ed material in this presentation to federal employees was marked For Of cial Use Only FOUO Please remove the OUO designation from the slides used at this presentation and make them available for public release The American people have a legitimate interest in understanding the extent to which US telephone networks are vulnerable to surveillance and are being actively exploited by hostile actors Sincerely Ron Wyden Cory Gar ier United States Sena United States Senator Edward J Mark Rand Paul United States Senator United States Senator This document is from the holdings of The National Security Archive Suite 701 Gelman Library The George Washington University 2130 H Street NW Washington D C 20037 Phone 202 994-7000 Fax 202 994-7005 nsarchiv@gwu edu