The Department of Homeland Security (DHS) believes that China, Russia, Iran, and Israel are the primary countries exploiting security holes in telecommunications networks to spy on people inside the United States, which can include tracking their physical movements and intercepting calls and texts, according to information released by Senator Ron Wyden.The news provides more context around use of SS7, the exploited network and protocol, against phones in the country. In May, 404 Media reported that an official inside DHSs Cybersecurity Insurance and Security Agency (CISA) broke with his departments official narrative and publicly warned about multiple SS7 attacks on U.S. persons in recent years. Now, the newly disclosed information provides more specifics on where at least some SS7 attacks are originating from.The information is included in a letter the Department of Defense (DoD) wrote in response to queries from the office of Senator Wyden. The letter says that in September 2017 DHS personnel gave a presentation on SS7 security threats at an event open to U.S. government officials. The letter says that Wyden staff attended the event and saw the presentation. One slide identified the primary countries reportedly using telecom assets of other nations to exploit U.S. subscribers, it continues.