WASHINGTON, May 18 (UPI) -- The United States' top intelligence official says there have been "some indications" of foreign hackers spying on the Democratic and Republican presidential candidates.
Clapper gave no details on the attacks, including who is behind them.
He said the Department of Homeland Security and the FBI "are doing what they can to educate both campaigns against potential cyber threats."
Presumptive GOP nominee Donald Trump has been hit by several hacks, including the defacing and spamming of campaign and business websites, and his Social Security number was released to the public.
Some hacker groups, including Anonymous, have threatened to launch "total war" against Trump's campaign.
Past presidential campaigns also have been hit by cyberattacks.
In 2008, Chinese agents targeted then-Sen. Barack Obama and Sen. John McCain in efforts to access their internal policy plans. In 2012, Obama and then-Republican presidential candidate Mitt Romney also dealt with attempted cyberattacks.
Clapper has said threats come from several fronts, including Iran, which has targeted U.S. banks and gained access to the computer system controlling a dam in New York.
He also pointed to attacks on Sony Pictures' employee files and email systems, and a suspected attack by China that led to the left of million of employee files from the federal Office of Personnel Management.
"The Russians and Chinese are far more sophisticated and could do real damage if so inclined. Then there are terrorist groups," Clapper said. "Each has different objectives. The one thing they have in common, they all operate on the same internet."
Clapper said he doesn't "recall a time when we've been beset by a wider array and more diverse array of threats and crises than we are today."
In remarks last month hosted by the Christian Science Monitor, Clapper said whistle-blower Edward Snowden, by leaking classified data two years ago, contributed to the acceleration of sophisticated encryption methods that militants are using to hide their communications.