Hillary Clinton admitted the State Department’s network was vulnerable to cyberattacks Sunday in an exchange that highlighted criticisms of her use of a private server while she was secretary of state.

“The State Department was attacked at least every day, if not several times a day while I was there,” Clinton said during an interview with a radio station in Boston. “Many of those were repelled by the security protections that were in the system, but we know there have been increasingly sophisticated attacks that are penetrating.”