Cybersecurity is a "very big issue" that DHS remains concerned about, said DHS Secretary Michael Chertoff, testifying before the House of Representatives Homeland Security Committee. Chertoff didn't go into details because much of the department's cybersecurity efforts are classified, he said.

"I can assure you that we are working with other elements of the federal government and giving highest priority an enhanced strategy with respect to cybersecurity," he said. Cybersecurity threats have "enormous potential to do damage to the United States in years to come," Chertoff added.

Chertoff testified before the committee in a hearing titled, "Holding the Department of Homeland Security Accountable for Security Gaps." But while cybersecurity problems continue in and outside of the U.S. government, lawmakers focused on other issues during the hearing, including the hiring of border agents, training of bomb-sniffer dogs and the scanning of airline cargo.

Just this week, the U.S. Department of Defense acknowledged a successful attack on an unclassified e-mail system earlier this year. (See E-Mail System Attack Caused No Damage, U.S. DoD Says.)

Committee chairman Bennie Thompson, a Mississippi Democrat, said DHS needs to improve in several areas. Thompson has criticized the department's cybersecurity efforts in the past, but cybersecurity issues were not on Thompson's list of top priorities for Chertoff in the remaining 16 months of U.S. President George Bush's administration.

Instead, Thompson called on Chertoff to fill vacancies at DHS, to finish regulations for container security at ports and to implement a biometric air passenger screening program.