Russia's goal isn't to shut down voting machines, but rather make Americans believe that their vote didn't count. The plan is being bolstered, perhaps unwittingly, by GOP candidate Donald Trump's recent statements that voters shouldn't believe some states' electoral results if he loses in November, Singer said.
"The goal is not to make people directly pro-Putin," Singer said. "The idea is to make people dubious of all information, to distrust democratic institutions. That's why it is so dangerous, and the narrative of a 'stolen election' feeds into this."
Russian disinformation has been commonplace in parts of the former Soviet Union, but it's also been happening in western nations like Sweden.
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One example of such effort of disinformation was the fake letter circulated on the web with a signature of the Swedish defense minister, Peter Hultqvist, according to Benedicte Berner, chair of the Stockholm-based group Civil Rights Defenders and faculty member at the Davis Center for Russian and Eurasian Studies at Harvard University.
In the letter, Hultqvist was congratulating the company BAE Bofors for a contract to sell guns to Ukraine. The fake document was traced as coming from St Petersburg.
"The Swedish intelligence service is now establishing a group to try to identify where such disinformation comes from and try to respond," Berner said in an e-mail to Discovery News. "This is a difficult task as the disinformation is spreading fast and is recurrent."
So what should U.S. officials do? Mark N. Kramer, a Russia expert at Harvard, says the American military possesses powerful cyber capabilities, but using them in all-out response would then reveal Pentagon secrets.
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"They U.S. needs to think carefully in advance, which they are doing now, about how and what sorts of steps to retaliate against detected Russian attempts," Kramer said. "It doesn't start out with an all-out strike."
Kramer said Russia's leaders ties to the international financial system make them vulnerable. "That's where I would see the initial response."
Singer said that there are other steps besides a "hack-back" from the U.S. side. It could involved leaking embarrassing information about the financial assets of people close to the Russian government, for example.
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"We could tell them that we know you have hidden assets in these London real estate locations, and if we reveal it, you will lose these assets," Singer said. "Going after a Russian oligarch and sending a message that we need to stop this."
Both experts noted that the best defense is better computer security by election officials in state and counties. Unfortunately, given irregularities in the 2000 election in Florida, and problems in some Ohio counties more recently, it's likely that we will see more trouble-making smudged with Russian digital fingerprints between now and Nov. 8.
"There has been mistrust in the past, particular after 2000," Kramer said about problems in Florida's vote count. "There is an electoral system that has vulnerabilities. It's fertile ground for mischief makers."