Washington (AFP)

Russia is "probably" at the origin of the gigantic cyberattack detected in December in the United States, concluded Tuesday the American intelligence services.

The FBI (federal police), the Directorate of Internal Intelligence, the NSA military agency and the US agency in charge of cybersecurity and infrastructure security (Cisa), thus contradict Donald Trump who accused China of being behind this intrusion into the software of the US government and thousands of private companies.

The investigation concluded that an "adversary, probably of Russian origin, is responsible for most of the recently discovered intrusions into governmental and non-governmental computer networks," the four intelligence services said in a joint statement.

"At this stage, we think it was and still is a spy operation" and not an attempt to sabotage infrastructure, they add.

"We are taking all necessary measures to assess the scale of this operation and respond to it."

The attack began in March, with hackers taking advantage of an update to monitoring software developed by a Texas company, SolarWinds, used by tens of thousands of businesses and governments around the world.

It continued for months before being discovered in December by the computer security group FireEye, itself the victim of cyber attacks.

But according to the intelligence services, "the number of compromised entities much lower" than 18,000.

"We have only identified a dozen government agencies" whose systems were hacked, the statement added.

The intelligence services did not specify which agencies had been affected, but several ministries have already reported intrusions, including the State Department, the Foreign Trade Department, the Treasury, or the Department of Homeland Security ( DHS).

Before Mr. Trump expressed doubts about Russia's guilt, U.S. Foreign Minister Mike Pompeo pointed the finger at Moscow, but U.S. Intelligence had so far refrained from naming a culprit.

"It is regrettable that it took more than three weeks for this administration (...) to finally publish a vague accusation," commented Democrat Mark Warner, vice-chairman of the Senate Intelligence Committee.

"I hope that we will soon have something more emphatic," he said, adding that Russia should be warned that these actions are "unacceptable and will receive a response on an appropriate scale".

© 2021 AFP