RUSSIA’S MEDDLING with democracy no longer comes as a surprise. It should, nevertheless, continue to provoke anger, outrage and a determination to respond.

Observers predicted that last month’s elections for European Parliament would offer a window on a new era of disinformation. Now, European Union officials have rendered a verdict that suggests the Kremlin kept itself busy — engaging not in any grand cross-border campaign but in sustained interference on a smaller scale that may be even harder to root out. Worse, others followed its lead.

The E.U. report and concurrent outside research show that the enemy is evolving. Gone are the days when vast networks of false-identity accounts and their automated counterparts worked en masse to spread tales of events that never occurred or malicious lies about public figures. Now, operations are more localized and harder to detect. They feature what experts call narrative warfare, pushing polarizing and distorted variations of otherwise true stories, stripped of context, rather than outright fabrications. The tactic is tougher both for platforms to detect and for governments to legislate against.

That gray zone poses particular difficulties when the perpetrators are domestic actors and transnational far-right groups that strategically blur the line between information operations and political campaigning. Those groups have seized on Russia’s successful methods to stymie platforms in their enforcement efforts, and, though sites have made progress, keeping up is not easy. Platforms’ internal systems to limit misleading political advertisements also often fall short, and researchers complain about insufficient access to data that would help them find and analyze disinformation operations going forward.

E.U. officials have said they may still seek to regulate social media sites to force them to invest more in fighting disinformation. Any such measures should focus on the mechanisms that platforms have in place to reduce the reach of manipulative content — not on punishing platforms for the content itself. The E.U. also should build on what authorities say worked well this time around: public education and coordination among sites, civil society and member states, including through a “rapid alert system,” to detect and debunk threats. Other countries with no coherent strategy to counter disinformation, including the United States, should take a lesson.

Most of all, those governments, and the United States’, should stay angry. Interference from Russia is a hostile act, and leaders must fight against shrugging it off as an inevitability. The announcement that an authoritarian power and those pulling from its playbook tried to undermine more than 500 million Europeans’ right to pick their representatives should spark defiance. From President Trump, it has sparked nothing. The lack of outrage is an outrage itself.

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