U.S. Secretary of Defense Pete Hegseth, including Vice President JD Vance, White House National Security Advisor Michael Waltz, Deputy Chief of Staff Stephen Miller, Secretary of State Marco Rubio, and CIA Director John Ratcliffe, among other senior officials responsible for national security, are under scrutiny after discussing airstrike operations against the Islamic militant group Houthi in Yemen in a group chat without knowing that Jeffrey Goldberg, editor of the magazine 'The Atlantic', had been invited. Interest is focused on the messenger 'Signal' used by these officials as they discussed military operations requiring security on a messaging platform used by the general public.
◇ Signal, developed with investment from WhatsApp co-founder, operated by a nonprofit organization, led by a former Google executive
Signal is known as an encrypted chatting app primarily used by federal government employees, journalists, Silicon Valley workers, and dissidents, offering free text, voice, and video chatting. Similar to regular messengers, it allows users to send messages, create group chats, and post disappearing stories like those offered by Instagram. There are no ads, and messages can be set to disappear after a certain time (ranging from 30 seconds to a maximum of 4 weeks). It can be used on both mobile phones and desktop computers.
Signal is owned by the nonprofit organization 'Signal Technology Foundation', located in Mountain View, California, and is primarily operated through donations and subsidies. The founder of Signal Technology Foundation, Moxie Marlinspike, who worked as a security chief at Twitter in 2014, was supported with $50 million (approximately 73.21 billion won) from WhatsApp co-founder Brian Acton to establish it. The reason for operating Signal Technology Foundation as a nonprofit organization is to ensure that Signal has no commercial motives to store or monetize user data. Signal is currently led by Meredith Whittaker, a former Google executive and co-founder of the AI Now Institute, who has served as the inaugural president since 2022.
Signal Technology Foundation paid over $5.5 million for cloud services from Amazon Web Services, Google, and Microsoft (MS) in 2023. Signal is available in 170 countries worldwide, and its servers are distributed across the globe. According to market research firm Sensor Tower, Signal was downloaded more than 2.7 million times in the U.S. alone this year, marking a 36% increase compared to the same period in 2024.
The most significant feature is the use of end-to-end encryption technology. This allows data to be encrypted during transmission, meaning that only the sender and receiver can view it. Theoretically, messages transmitted over the Internet cannot be understood by others. Even if hacked or if the government brings a subpoena demanding information about users, only the date the account was created and the last accessed time can be provided. The date the message was sent and to whom it was sent cannot be determined.
So far, there is no evidence that Signal's open-source encryption algorithm has been compromised. Encryption experts have suggested that Signal could be the safest encryption app available for use on regular mobile phones. However, Matthew Mittlestadt, a technology policy researcher at the Cato Institute, a U.S. think tank, noted to CNN that 'While messages sent via Signal may be secure while transmitting between phones, security could be compromised once they reach the recipient.' The Washington Post (WP) also reported that 'Despite using end-to-end encryption, messages can still be viewed on both the recipient's and sender's end, which means that if there is hacking or a cyberattack, messages on the mobile phone could be exposed,' adding that 'spyware installed without the phone owner's knowledge could take screenshots of messages and bypass Signal's encryption system.'
◇ “Many employees of the Trump second administration, of course, members of the Biden administration also use Signal”
Federal government employees are known to have predominantly used Signal during the Trump second administration. WP quoted over 20 federal employees, speaking on condition of anonymity, stating, 'Federal employees and officials have been using Signal for communication since Trump took office,' and added that 'The only tool that allows them to communicate with family, colleagues, and journalists without being monitored by the government regarding federal workforce reductions is Signal.'
This is not the first time Signal's usage has become an issue since President Donald Trump's return to power. Federal judges confirmed that DOGE employees were discussing work-related matters via Signal in a trial related to the Department of Government Efficiency (DOGE), led by Tesla CEO Elon Musk.
The Associated Press reported that during the Biden administration, federal government employees also used Signal to schedule sensitive meeting agendas or have confidential phone calls outside the office. The Associated Press stated that 'Signal was used more widely during the last year of the Biden administration after federal law enforcement agencies warned that China and Iran were hacking not only Trump’s first administration officials but also the White House.'
◇ Trump: “I will probably not use Signal much in the future”
National security experts point out that discussing classified information on an app designed for general use on mobile phones violates security protocols and poses a high risk of information leaks. Mobile phones are always exposed to hacking risks, and individuals are advised not to share classified information on personal smart devices.
Typically, discussions related to classified military plans are conducted only in secure compartmented information facilities (SCIF). SCIF is a room designed to prevent third parties from eavesdropping on conversations. The use of mobile phones, which can be hacked, as well as other electronic devices is prohibited in SCIFs. Most SCIFs are located in federal government offices and embassies also have secure facilities. High-ranking officials in charge of national security also have personal SCIFs in their residences to discuss sensitive matters 24/7.
Meanwhile, the National Security Council is investigating how editor Goldberg was added to the group chat. The subjects of the investigation include Secretary of Defense Hegseth, Vice President JD Vance, Secretary of State Rubio, and National Intelligence Director Tulsi Gabbard, among others. However, Trump downplayed the incident in an interview with NBC News on the 25th, describing it as 'the only error that occurred in the two months since the inauguration of the Trump second administration' and concluded that 'it was determined not to be a serious error.' Nevertheless, Trump stated during a Q&A session with reporters at the White House on the 25th that 'We probably won't be using Signal much moving forward,' indicating an intention to limit the use of Signal.