But facts have been powerless against a torrent of abuse and ridicule targeted at European journalists, researchers and others labeled NATO stooges.

Pro-Russian activists insist that they are merely exercising their right to free speech, and that they do not take money or instructions from Moscow.

The most abusive messages against Ms. Aro were mostly sent anonymously or from accounts set up under fake names on Facebook and other social media.

One of her most vocal critics in Finland, however, has openly declared his identity. He is Johan Backman, a tireless supporter of President Vladimir V. Putin of Russia who highlights the blurred lines between state-sponsored harassment and the expression of strongly held personal views.

Fluent in Russian, Mr. Backman now spends much of his time in Moscow, appearing regularly in the Russian news media and at conferences in Russia as “a human rights defender.” He also serves as the representative in Northern Europe for the Russian Institute for Strategic Studies, a state-funded research group led by a Soviet-era intelligence officer.

Mr. Backman, who also represents the Donetsk People’s Republic, the breakaway state set up with Russian support in eastern Ukraine, denied targeting Ms. Aro as part of any “information war.” Rather, he insisted that Russia was itself the victim of a campaign of disinformation and distortion conducted by the West.

In a recent interview in Moscow, he said that Ms. Aro was part of this campaign and that she had tried to curtail the freedom of speech of Russia’s supporters in Finland by labeling them as “Russian trolls.” All the same, Mr. Backman added, her complaints about being targeted for abuse “have been very beneficial for Russia” because they have made others think twice about criticizing Moscow.