Former senior Clinton adviser Justin Cooper repeatedly professed that he could not provide specific details about the security protections in place on Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE’s private email server during a Tuesday congressional hearing.

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Pressed by lawmakers on whether the contents of the server were encrypted and required dual-factor authentication in order to gain access, Cooper deferred, saying that he was not an IT expert.

“I unfortunately cannot provide you with the details of what the specific security functions on the server. I know there were security functions on the server and they evolved over time as technology evolved over time,” Cooper said during an at-times heated hearing on State Department records before the House Oversight Committee.

The former senior adviser to President Bill Clinton William (Bill) Jefferson ClintonGOP brushes back charges of hypocrisy in Supreme Court fight Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE set up Hillary Clinton’s email account on the server and registered the original clintonemail.com domain name.

Cooper said that Clinton, now the Democratic nominee for president, did with “some frequency” experience failed brute-force attacks on the server, in which hackers would attempt to gain entry by repeatedly testing random combinations of usernames and passwords.

“We developed systems to tamp those down,” Cooper said.

He said he did not recall whether the server was encrypted and did not think that it had dual-factor authentication, sparking outrage amongst Republicans.

“I’m very grateful for your candid nature in expressing the idea that you don’t have the expertise to answer those questions as thoroughly as possible,” Chairman Jason Chaffetz Jason ChaffetzThe myth of the conservative bestseller Elijah Cummings, Democratic chairman and powerful Trump critic, dies at 68 House Oversight panel demands DeVos turn over personal email records MORE (R-Utah) said.

“The problem I have [is that] it’s you, Mr. Cooper, with no experience, no encryption, no dual authentication, up against the Chinese and the Russians. Who do you think’s gonna win that one? That’s what scares the daylights out of me.”

Some Democrats pushed back, arguing that Republicans were trying to force witnesses to “disprove a negative.”

“The repetition of the question raises the apprehension that the Chinese or the Russians are making this determined effort to hack into accounts and focusing it all on Hillary Clinton acts as though that intentionality of the Russians and the Chinese doesn’t apply across the board to anybody and everybody that’s in government,” said Rep. Peter Welch Peter Francis WelchShakespeare Theatre Company goes virtual for 'Will on the Hill...or Won't They?' Vermont Rep. Peter Welch easily wins primary Vermont has a chance to show how bipartisanship can tackle systemic racism MORE (D-Vt.).

Whether or not Clinton’s server was hacked by foreign adversaries has been a focal point of debate over her use of a personal server while secretary of State.

In his summary of the results of FBI’s investigation, Director James Comey said that it is “possible” Clinton’s server was hacked.

Federal investigators found no direct evidence that hackers had managed to break into the server or access the email account hosted on it, he said in his announcement that the FBI would not recommend charges against Clinton.

“But, given the nature of the system and of the actors potentially involved, we assess that we would be unlikely to see such direct evidence,” Comey said.

“Given that combination of factors, we assess it is possible that hostile actors gained access to Secretary Clinton’s personal email account.”

The State Department IT technician and two employees of the Denver-based firm that maintained the server pleaded the Fifth Amendment and refused to answer questions on the server during the same hearing.