Joel Brenner, Former National Security Agency inspector general and senior counsel, warned against the increasing vulnerability of American cyber society last night at the Cambridge First Parish Church.

Brenner’s remarks were based on  his new book, “America the Vulnerable,” which discusses the dangers that the lack of technological privacy may pose to governments, corporations, and individual citizens.

People make themselves vulnerable everyday, he said, citing discount grocery cards, credit cards, EZ-Pass, and particularly file sharing programs as technologies that “leave footprints” of a person’s activity.

A lack of security consciousness can have grave consequences, he said. For example, the flight plan of the presidential helicopter was once leaked to Tehran after a Defense Department employee used a file-sharing program on a government computer, according to Brenner.

Brenner, who graduated from Harvard Law School, said he wrote the book after his work in the government led him to realize how little the American public understands about the security risks of sharing information through technology.

“[We are] electronically naked without even knowing it,” he said. “[But] we love this connectivity. We embraced this world.”

Brenner emphasized that the increasing digitization of information could lead to new and dangerous forms of espionage.

“Joshua sent spies into the Holy Land. This is not new,” he said, referencing the biblical story in the book of Numbers. “[But] now you don’t need a spy, you can steal information remotely.”

Brenner outlined the increasing capabilities of modern cyber-theft and espionage, stressing the possible international consequences.

“When someone steals your car and you go outside, you know it’s gone,” he said, “When someone steals a trade secret, you still got it.”

It could take years, Brenner said, to realize that another country or company has stolen information.

“We’ve both embraced it and it makes us uncomfortable,” he said of cyber insecurity.

“How does one begin to come to grips with technology that is wonderful and also taking off our clothes to a certain extent?”

Brenner compared the risks of transferring technological information to the exchange of sexually transmitted diseases.

“Take a USB,” he said, “you don’t know where it’s been and you stick it in your USB drive, where was that last night?”

Brenner said that the underlying problem is the average user’s willingness to share potentially sensitive information.

“When security butts heads with convenience, which it does all the time, convenience wins,” Brenner said.