In his final days as the 44th president of the United States, Barack Obama authorized a covert hacking operation to implant attack code in sensitive Russian networks. The revelation came in an 8,000-word article The Washington Post published Friday that recounted a secret struggle to punish the Kremlin for tampering with the 2016 election.

According to Friday's article, the move came some four months after a top-secret Central Intelligence Agency report detailed Russian President Vladimir Putin's direct involvement in a hacking campaign aimed at disrupting or discrediting the presidential race. Friday's report also said that intelligence captured Putin's specific objective that the operation defeat or at least damage Democratic candidate Hillary Clinton and help her Republican rival Donald Trump. The Washington Post said its reports were based on accounts provided by more than three dozen current and former US officials in senior positions in government, most of whom spoke on the condition of anonymity.

In the months that followed the August CIA report, 17 intelligence agencies confirmed with high confidence the Russian interference. After months of discussions with various advisors, Obama enacted a series of responses, including shutting down two Russian compounds, sanctioning nine Russian entities and individuals, and expelling 35 Russian diplomats from the US. All of those measures have been known for months. The Post, citing unnamed US officials, said Obama also authorized a covert hacking program that involved the National Security Agency, the CIA, and the US Cyber Command. According to Friday's report:

The cyber operation is still in its early stages and involves deploying “implants” in Russian networks deemed “important to the adversary and that would cause them pain and discomfort if they were disrupted,” a former U.S. official said. The implants were developed by the NSA and designed so that they could be triggered remotely as part of retaliatory cyber-strike in the face of Russian aggression, whether an attack on a power grid or interference in a future presidential race. Officials familiar with the measures said that there was concern among some in the administration that the damage caused by the implants could be difficult to contain. As a result, the administration requested a legal review, which concluded that the devices could be controlled well enough that their deployment would be considered “proportional” in varying scenarios of Russian provocation, a requirement under international law. The operation was described as long-term, taking months to position the implants and requiring maintenance thereafter. Under the rules of covert action, Obama’s signature was all that was necessary to set the operation in motion.

The intelligence agencies reportedly don't need Trump's approval to continue the operation, although Trump could stop it by issuing a countermanding order. So far, officials told the Post, they haven't seen any indication Trump has done so.