How 'Home Brew' Email Servers Like Hillary Clinton's Work

— -- An email server such as the one Hillary Clinton used may conjure up an image of refrigerator-sized machines and tangled wires, but the home brew server used during Clinton's tenure as secretary of state is likely no bigger than a desktop computer.

Setting up a so-called home brew server is something that requires strong technical expertise and upkeep but can bring tremendous privacy and security to users, Robert Siciliano, an online safety expert to Intel Security, told ABC News.

"There are many plug-and-play products you can purchase, but there is still a lot of maintenance and upkeep to keep one functional and operational," Siciliano said. "You need to know what you’re doing."

Clinton has directed her staff to hand over to the Department of Justice the private email server that she used during her tenure as secretary of state, a campaign spokesman said Tuesday night. The move comes amid a federal investigation into the security of the server and whether there was classified information in the emails. Clinton's team has also turned over a thumb drive containing emails that has already been provided to the State Department, according to a campaign official.

Setting up her own email server added another layer to help Clinton keep her correspondence away from potential prying eyes. Every time the typical email user without their own server fires off an email message, a copy of that correspondence resides on their email carrier's server, which then connects with the recipient's server to deliver the message.

"Whoever hosts your email, whether it's your Internet service provider or any of the cloud-based carriers, in some way, shape or form, there is someone or a team of people who have access to your communication," Siciliano said.

While technical details about the hardware Clinton used are unknown, Siciliano said setting up a typical private server can cost anywhere from a few hundred dollars to several thousand dollars, making it a worthwhile expense for privacy-minded individuals.

"You need to know what you’re doing and there is some programming involved," Siciliano said. "It's not for the faint at heart."

When the issue of Clinton's email habits as secretary of state first came to light in March, she explained she chose to use a personal account out of convenience and added that all of her business-related emails were going to state.gov employees, making them a part of the official record.

"Looking back, it would have been better if I'd simply used a second email account and carried a second phone," she said in March. "But at the time, this didn't seem like an issue."

ABC News' Liz Kreutz contributed to this report.