Defense Secretary Pete Hegseth used the Signal app on a personal computer in his office that was connected to the internet on an unsecured commercial line, what’s known as a “dirty line,” two sources confirmed to ABC News Thursday.

A “dirty line” is the nickname given to a commercial internet line that is used to connect to websites that would not be available on the Pentagon’s unclassified (NIPR) or classified (SIPR) lines.

This dirty line was installed at Hegseth’s request so he could use the Signal app on the personal computer, the sources said.

A commercial internet line does not have any of the firewall protections that the Defense Department’s unclassified system has, so that makes it potentially susceptible to being monitored particularly if sensitive information is being communicated.

The news was first reported by The Associated Press.

Reached for comment about the existence of the dirty line in Hegseth’s office, a DOD spokesperson referred to an earlier statement from Sean Parnell, the Pentagon’s chief spokesperson.

“The Secretary of Defense’s use of communications systems and channels is classified,” said Parnell. “However, we can confirm that the Secretary has never used and does not currently use Signal on his government computer.”

This is a developing story. Please check back for updates.