Warning that the longest government shutdown in U.S. history may have opened the U.S. up to new national security risks because of undetected cyberattacks, Democratic lawmakers on Tuesday pressed the Trump administration to explain how furloughs disrupted efforts to defend federal computer systems from hackers.

Six Senate Democrats sought answers from senior administration officials about how the government will overcome delays in contracts with firms that safeguard U.S. networks. They also worried that, during the shutdown, agencies weren’t able to quickly implement an emergency Department of Homeland Security order to secure web traffic.

The lawmakers also expressed alarm about the shutdown’s effect on the morale of federal cybersecurity workers, especially as Washington struggles to compete with the private sector for top talent.