What is a SCIF? Inside the high-security rooms that keep military secrets safe — unlike a Signal chat

The US government invests billions in building Sensitive Compartmented Information Facilities, or SCIFs (pronounced "skiff")— highly secure rooms designed to safeguard sensitive discussions and operations from hacking and foreign surveillance.

US military and intelligence officials use these SCIFs to have classified conversations about military strategy, intelligence gathering, and diplomatic negotiations.

These facilities can be used to discuss any level of classified material, but they are specifically for Top Secret/Sensitive Compartmented Information (TS/SCI).

SCIFs can vary in size from a small room to an entire building, and the average cost per square foot for one of these rooms ranges between $350 and $1,000.

Federal agencies like the CIA and NSA, as well as some US embassies and government offices, have SCIFs within their buildings.

The US Capitol has a SCIF where congressional committees can host closed meetings or hearings. The SCIF in the White House — commonly referred to as the Situation Room — is one of the most well-known examples of a secure room. It's where the president and senior staff are often photographed monitoring significant international crises or coordinating US military operations overseas.

SCIFs are also constructed at some US military bases, either in permanent installations or within temporary facilities like shipping containers or tents.

Hotel rooms and temporary accommodations for the president and other high-ranking government officials can often become SCIFs so they can participate in classified conversations at a moment's notice. In 2017, President Donald Trump and his security team set up a makeshift situation room at his Mar-a-Lago resort to monitor the US strikes on Syria.

Some Cabinet-level members even have rooms in their homes converted into SCIFs equipped with essential government-approved teleconference equipment.

US intelligence agencies have strict requirements for maintaining the airtight security expected from SCIFs, including restricting the construction of the secure rooms to American companies.

Some SCIFs only allow personnel with proper security clearances to enter, restricting unauthorized access with security measures such as armed guards, biometric access, and 24/7 surveillance. Documents and other information remain confined inside the secure walls of the facility.

Inside a SCIF, phones, laptops, smartwatches, and other communication devices are prohibited. People new to a SCIF often mistakenly bring their personal devices in and have to be instructed to step back out and put them in a locker or other storage option.

The reinforced walls of a SCIF are typically soundproofed to prevent outside physical eavesdropping and covered in signal-shielding materials designed to control and block electronic eavesdropping.

Military officials are required to use government-approved compartmentalized environments like SCIFs for the highly sensitive information they handle.

SCIFs enforce strict "need-to-know" protocols, reducing the risk of unauthorized access, unlike chat apps where users can accidentally be added or hackers can force their way inside.

While Signal features the same kind of end-to-end encryption used by the US government, it can still be compromised. The app's popularity among troops and government officials makes it a prime target for hacking groups, prompting the Pentagon to issue an advisory on the vulnerabilities of the digital platform just days before The Atlantic published its initial bombshell report.

"It was a chilling thing to realize that I've inadvertently discovered a massive security breach in the national security system of the United States," Goldberg told NPR in the aftermath.

President Donald Trump downplayed the serious national security breach as a "glitch" and said that no classified information was discussed in the chat, which was called "Houthi PC small group," PC standing for "principals committee."

Hegseth doubled down on that particular point, arguing that "nobody was texting war plans" in the Signal chat. Michael Waltz, Trump's national security advisor who added Goldberg to the group, took "full responsibility" for the "embarrassing" security breach.

"There's a difference between inadvertent release versus careless and sloppy, malicious leaks of classified information," Director of National Intelligence Tulsi Gabbard testified during a congressional hearing.

In response to these characterizations of the chat, The Atlantic later released the messages almost completely unredacted to allow people "to reach their own conclusions" about the significance of the content.

The group chat included details like types of weapons to be used and expected times of impact, as well as strategic discussions over the duration of the operation.

"There is a clear public interest in disclosing the sort of information that Trump advisors included in nonsecure communications channels," The Atlantic wrote in the follow-up report, "especially because senior administration figures are attempting to downplay the significance of the messages that were shared."