Russian hackers have not stopped targeting U.S. political organizations and other American institutions in the weeks following Election Day, according to CNN.

Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE’s presidential campaign, prominent think tanks and other American organizations are the target of an ongoing cyber campaign linked to the Kremlin, which was blamed for interference in the presidential election, officials told the news outlet.

"It's not like the one and done deal here,” one U.S. official told CNN. “They continue to engage in this operation around the clock."

The operation targeting Clinton’s campaign, which reportedly was ongoing as recently as this month and included phishing attempts designed to trick staffers into downloading malicious software, was unsuccessful, investigators told the news organization.

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The new report is likely to deepen concern about the extent of Moscow’s attempts to influence and undermine the American political system, which have become a topic of increasing scrutiny in recent weeks.

The nation’s intelligence agencies have claimed that for several months hackers with ties to the upper reaches of the Russian government were engaged in a protracted hacking campaign to disrupt the U.S. election. According to several reports, the operations were overseen by President Vladimir Putin and were eventually designed to support President-elect Donald Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE and tear down Clinton. Democratic outfits including the Democratic National Committee were the target of hackers who leaked stolen documents onto the internet.

President Obama has pledged to retaliate against the Russian activity, although the administration appears conflicted about how to respond.

“Right now it's like the old cold cyber war and the last thing you want to do is turn it into a hot shooting war,” the unidentified official told CNN.