The Department of Homeland Security?s Response to
Senator Ron Wyden?s November 17, 2017 Letter

1. Has DHS seen any evidence of foreign IMSI catchers operated in the National Capital

Region?
a. If yes, was this evidence reported to any congressional committees?

The Department of Homeland Security?s (DHS) National Protection and Programs Directorate
(NPPD) has observed anomalous activity in the National Capital Region (NCR) 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. This information was reported

to our Federal partners at the time it was observed.

2. Does DHS agree that foreign government use of IMSI catchers in the National Capital
Region poses a threat to US. national and economic security

Information regarding the sources and methods that foreign governments use to conduct
intelligence activities is generally classi?ed. NPPD believes the use of these devices by
malicious actors to track and monitor cellular users would be unlawful and threaten the security
of communications, resulting in safety, economic, and privacy risks. NPPD agrees that the use
of IMSI catchers by foreign governments may threaten US. national and economic security.

3. Does DHS currently have the technical capability to detect foreign IMSI catchers in the

National Capital Region?
a. If yes, has DHS deployed assets capable of detecting foreign IMSI catchers in the

National Capital Region?
b. If no, what would DHS need to have this technical capability?

NPPD is not aware of any current DHS technical capability to detect IMSI catchers. To support
such a capability, DHS would require funding to procure, deploy, operate and maintain the
capability, which includes the costs of hardware, software, and labor.

4. Has DHS seen evidence of foreign IMSI catchers in other major US. cities and does
DHS agree that foreign IMSI catchers in other cities would pose a serious threat to US.

national and economic security?
a. If DHS has seen evidence of foreign IMSI catchers in other major US. cities,

what steps has DHS taken to respond?

NPPD is aware of anomalous activity outside the NCR that appears to be consistent with IMSI
catchers. NPPD has not validated or attributed this activity to speci?c entities or devices.
However, NPPD has shared this information with Federal partners

5. Native 4th Generation IMSI catchers are now openly advertised by
surveillance technology companies. Does DHS currently have the technical capability

to detect IMSI catchers?

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a. If not, what resources, if any, has DHS invested to address this advanced
surveillance threat?

NPPD is not aware of any current DHS technical capability to detect IMSI catchers. To

support such a capability, DHS would require funding to procure, deploy, operate and maintain
the capability, which includes the costs of hardware, software, and labor.

March 2018 Page 2