Booz Allen Hamilton said Thursday that it has hired Robert Mueller, a former FBI director, to conduct a review of the firm's security processes after one of its employees was charged with stealing huge amounts of classified data from the National Security Agency.

"We take the trust clients place in us seriously and are proud to support our country's important national security missions," Craig Veith, Booz Allen's vice president for external relations, said in a statement. "We are committed to doing our part to detect potential insider threats, which are complex and constantly evolving."

In a complaint that was unsealed this month, Harold Martin was charged in what is alleged to be one of the largest thefts of classified material in U.S. history. Martin's arrest follows the leaks of Edward Snowden, who also worked for Booz Allen while on contract to the NSA and walked away with troves of sensitive information.

Prosecutors have said that Martin took at least 50 terabytes of digital data, or as much as 500 million pages of information. He also had six boxes of files, many of which were left open in his house or car, prosecutors said.

Also on Thursday, in documents urging that Martin remain jailed, prosecutors alleged that they found the names of U.S. intelligence officers in the materials they recovered from Martin, which posed a particular threat to the safety of those operating undercover abroad. They said Martin's communications were being monitored - except with his lawyers - and they remained concerned about the damage he could do if he was able to reveal any of the information he took.

Last week, Martin's attorneys painted a different picture of their client, saying he was not like Snowden, who leaked information on sensitive surveillance programs to journalists, including at The Washington Post. Rather, they described Martin as a "voracious reader committed to being excellent at his work."

Gathering the information "began as an effort to be better at his job," his attorney, James Wyda, told a U.S. magistrate judge last week.

On Friday, Martin is due back in federal court in Baltimore. His defense attorneys will argue that Martin is not a flight risk and should be released from jail. They are appealing a magistrate judge's ruling from last Friday that Martin continue to be detained.

McLean-based Booz Allen said that it fired Martin as soon as it learned that he was arrested and that the company has been fully cooperating with the FBI.

In the statement, Veith said the company is confident that Mueller "will conduct a fair, objective, and thorough review ... We are an organization that prides itself on constant learning. If there are areas where Booz Allen can improve, we will address them."

In an email to employees Thursday afternoon that was obtained by The Post, Booz Allen's chief executive officer, Horacio Rozanski, praised Mueller's "unparalleled reputation for integrity." Rozanski said that Mueller "has been given broad authority to go where the review takes him and come back to us with recommendations."

The review began on Oct. 19, Rozanski wrote.

The company was founded in 1914 and has a long history working for the U.S. military. It began its government service by advising the secretary of the Navy in 1940 in preparation for World War II. Today, about 30 percent of the company's workforce of 22,600 people are veterans, including 48 senior leaders, the company says, and nearly 70 percent hold security clearances, according to a filing with the Securities and Exchange Commission.

In fiscal year 2016, 97 percent of the company's revenue came from the U.S. government through more than 5,000 contracts, according to the filing. Its biggest customer was the Army. Nearly half of the company's revenue - $2.6 billion - came from defense clients, and a quarter, or $1.3 billion, came from intelligence customers, such as the NSA. Seven of its 10 most lucrative contracts were classified.

The company has long and deep ties to many of the nation's most secretive agencies, including the National Geospatial Intelligence Agency, the National Reconnaissance Office and the Defense Intelligence Agency, and its employees often work alongside government employees at such organizations. In 2013, after the Snowden incident, an article in Bloomberg called it the "world's most profitable spy organization" and noted that James Clapper Jr., the director of national intelligence, is a former executive at the company.

In the filing, the company noted its reliance on the U.S. government and said that "if our relationships with such agencies are harmed, our future revenue and operating profits would decline."

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Ellen Nakashima and Matt Zapotosky contributed to this report.