The sheer volume of mobile phones, laptops and tablets used by federal officials is making it difficult to stop leaks of classified information, officials worry.

The controversy over Hillary Clinton Hillary Diane Rodham ClintonHillicon Valley: FBI chief says Russia is trying to interfere in election to undermine Biden | Treasury Dept. sanctions Iranian government-backed hackers The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters FBI chief says Russia is trying to interfere in election to undermine Biden MORE's private email has drawn fresh scrutiny to the handling of classified information.

While Clinton's is a high profile and somewhat unusual case, officials say federal employees across the board are struggling to keep security practices apace with rapidly evolving technology.

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The prevalence of email and the dramatic growth of the national security state simply makes leaks all but inevitable, they say.

“In this world, with the amount of communication, with the Internet, there’s so much that’s out there,” said Rep. Dutch Ruppersberger (Md.), formerly the top Democrat on the House Intelligence Committee.

The leaking of classified information — whether within the government or to the public — is infrequent but not unusual, officials say.

“Does it happen? Yes. Does it happen more than rarely? Yes. Does it happen regularly? No, it doesn’t,” said John Cohen, who worked in intelligence posts under both Presidents George W. Bush and Obama.

The government has long struggled with how to handle potentially sensitive information, torn between calls for transparency and the need to keep operations secret.

This high-wire routine only became more difficult with the proliferation of email and text messaging, and the many devices — BlackBerries, iPhones, iPads, laptops — people now use to chat.

Those dealing with official government secrets also have to use multiple computers that operate on different networks — unclassified, secret and top secret, in ascending order of sensitivity — as well as switch between phones for various conversations.

One senior Hill staffer who regularly handles classified information described the rigorous steps taken to keep things secret as the hardest part of the job.

A former National Security Agency official estimated he spent roughly 75 percent of his time on classified networks, occasionally defaulting to them to eliminate the threat of leakage.

The multiple modes of communication can be especially hard on diplomats overseas, who may need to send a secure message from isolated parts of a developing country, far away from secure lines.

“This is one of the reasons why you a have a temptation to kind of skirt around the rules,” said Greg Thielmann, a former foreign service officer and ex-aide to the Senate Intelligence Committee. “You have urgent information that needs to be conveyed, decisions have to be made. So you have to do your best.”

On unclassified systems, officials often have to rely on their best judgment to flag potentially classified material. For many, information from intelligence agencies intermingles with think tank and public news reports. Discerning, days later, which tidbits came from the CIA and which were from The New York Times can be a maddening process.

Ruppersberger said it takes time to fully understand the abstract classification rules.

“You do the best you can and the longer you work in that field, the more that you understand what is and what isn’t [classified],” he said.

Classified information is transmitted over a secret network, known as SIPRNet, or a top-secret network, JWICS. Both operate on walled-off, encrypted systems unconnected to the broader Internet.

But these networks are for the executive branch. Capitol Hill relies on yet another separate, secure network, called CapNet, adding another wrinkle to the complicated scheme.

Given these complexities, congressional committees actually receive the vast majority of their classified details the old fashioned way — on paper from a courier — and scan select pages into secure systems.

The House Intelligence Committee, one of Congress’s major handlers of classified information, also maintains its own internal computer network and secures its meeting room with round-the-clock uniformed officers. A full-time security director ensures only necessary staff are looking at each classified program.

Individual members don’t even have personal staffers with top secret security clearance. Instead, they are forced to rely on committee employees, a practice some lawmakers criticize.

“Public service is a public trust, and part of that trust is safeguarding classified information,” said Rep. Adam Schiff Adam Bennett SchiffOvernight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Overnight Defense: House to vote on military justice bill spurred by Vanessa Guillén death | Biden courts veterans after Trump's military controversies Intelligence chief says Congress will get some in-person election security briefings MORE (D-Calif.), the ranking member of the Intelligence panel. “Nowhere is this grave responsibility taken more seriously — and emphasized more regularly — than in the House Intelligence Committee.”

Yet even as the means of transmitting messages multiplied, the actual number of new classified documents shrunk dramatically after President Obama entered office in 2008.

Despite a rapid increase in official secrets following the Sept. 11, 2001, terror attacks, the amount of new material deemed sensitive was lower in fiscal 2014 than it had been in decades, according to theNational Archives Information Security Oversight Office.

Worries about potential leaks came to a head with the controversy over Clinton's email.

Her supporters say she fell victim to an increasingly complex set of classification rules and intelligence agencies’ tendency to classify anything they can.

But unlike other officials, Clinton relied solely on a private email server throughout her tenure at the State Department, and roughly one in 15 of the approximately 30,000 messages on her machine have been marked as classified.

“I think there’s no one who works in the national security space who doesn’t have something like that in their inbox,” said Mieke Eoyang, a former Dem House aide, now vice president for the national security program at the center-left think tank Third Way.

The FBI and a pair of federal inspectors general are investigating whether she or her top aides intentionally mishandled classified information.

Her critics acknowledge some leaks might be inevitable for senior officials.

“But it would happen more because of carelessness or thoughtlessness," said Patrick Eddington, a veteran of the CIA and House.

“That’s what appears to be a very, very different animal that we’re dealing with here in Clinton’s email-gate,” he alleged. “There was clearly a systematic policy in place to ensure that information was given to the secretary over an unclassified system.”

But Ruppersberger, who has endorsed Clinton's bid, says the challenge of handling classified information has simply become overwhelming.

“I’m sure we all make mistakes,” he said. “It’s a matter of volume.”