Hackers have attempted more than a dozen attacks on HealthCare.gov, the struggling website at the center of President Obama's signature healthcare law, according to published news reports citing a top US official.

All of the attacks, which occurred from November 6 through November 8, failed and remain under investigation, Acting Assistant Homeland Security Secretary Roberta Stempfley of the Office of Cybersecurity and Communications told a US House of Representatives committee Wednesday. She said she was also aware of the recent discovery of software designed to overload HealthCare.gov with more traffic than it could handle. As was the case when it was first spotted last week, there's no evidence that the DIY denial-of-service tool was ever actively used.

"We received about 16 reports from HHS that are under investigation and one open source report about a denial of service," Stempfley told members of the House Homeland Security Committee, according to this report from CNN.

In a separate hearing, a top HHS official said his department arranged for the site to undergo a "penetration test," in which a paid security consultant attempts to break into it using the same techniques used by malicious hackers. The test uncovered seven to 10 weaknesses related to security, Frank Baitman, CIO of HHS said. The social security numbers, e-mail addresses, phone numbers, birth dates, and other personal information collected by the site make it a high-value target for financially motivated attackers. Reuters has separate coverage here.