While answering questions during his hearing before the U.S. Senate Intelligence Committee on Thursday, former FBI Director James Comey testified Russian hackers targeted “hundreds” of entities in an attempt to interfere with the 2016 U.S. presidential election.

"There was a massive effort to target government and near-governmental agencies, like nonprofits," Comey said. When asked how many entities were targeted by Russians attackers, Comey said, “It's hundreds. I suppose it could be more than a thousand, but it's at least hundreds."

Read: What James Comey Will Say At Hearing About Trump, Russia And Mike Flynn

Comey’s insight into how widespread Russia’s hacking efforts appeared to fall in line with the conclusion of a recently leaked U.S. National Security Agency document published by the Intercept that showed a number of private election software and hardware manufacturers were targeted by the Russian military.

The document stated at least one voting software maker was compromised in a cyberattack. It also stated more than 100 local government officials and organizations involved with elections were targeted though there was no indication votes were manipulated.

Comey offered a similar conclusion regarding vote totals. When asked by committee chairman Sen. Richard Burr, R-N.C., if he was confident no votes were altered in the 2016 election, Comey said: “I’m confident. When I left as director, I had no indication of that whatsoever.”

The ousted FBI director also said his first indication of Russian efforts to interfere with the electoral process in the U.S. started as early as the summer of 2015.

Read: James Comey Testimony Hearing: What Security Experts Hope To Learn About Russian Hacking From His Remarks

Comey’s timeline and description of the breadth of the apparent cybercampaign carried out by the Russian government falls in line with much of what has been reported about the attacks, including details in the NSA document.

An analysis published by security research firm SecureWorks, which has tracked the Russian hacking group Fancy Bear that is supposedly behind some of the attacks, found that nearly 9,000 phishing links designed to compromise a person’s account were sent to around 4,000 individuals from October 2015 to May 2016. The dates and numbers match up to Comey’s testimony.

The former head of the FBI also said he expected the interference aimed at the 2016 presidential election will not be the last time the Russian government attempts to meddle with the U.S.

Comey called Russian hacking "a long term practice of theirs," and warned "they'll be back." He noted the hacking efforts were not necessarily aimed at advantaging a particular point of view, but rather were designed to sow chaos within the American government.

“They’re going to come for whatever party they choose to try and work on behalf of, and they’re not devoted to either, in my experience,” Comey said. “They’re just about their own advantage and they will be back.”