Several Democratic presidential campaigns targeted by a Russia-based operation on Facebook’s popular Instagram app said they had been unaware of the new foreign disinformation efforts until the tech giant announced them publicly last week, raising alarms that American democracy remains vulnerable to foreign interference even after three years of investigations into the Kremlin’s attack on the 2016 election.

The lack of advance notice to the apparent victims of the first known Russian attempts to interfere directly in the 2020 race has heightened fears that campaigns are largely on their own when it comes to guarding against attacks from foreign interests.

Campaign officials, security experts and Democratic lawmakers said the latest material served as a warning that the Trump administration and the tech industry are still struggling to coordinate their response as threats to the U.S. political system intensify. In particular, the threats now emanate from multiple countries, including Iran and China, where malicious actors have adopted Russia’s playbook in a bid to manipulate social media to their political advantage.

Some said they were unnerved by the nature of the recent Instagram posts, which seemed to target battleground states and demonstrated a nuanced understanding of the dynamics at play in the 2020 Democratic primary race. They appeared, for instance, to stoke African American resentment of former vice president Joe Biden while tapping into themes designed to undercut Sens. Elizabeth Warren (Mass.) and Kamala D. Harris (Calif.) as well. The Russian network appeared to be relatively small and in an audience-building mode, analysts said.

“The Russians are repeating the same tactics they used during the 2016 election, but only growing more strategic in identifying divides and capitalizing on those divides to create fault lines in society and distrust between people and institutions,” said Ali Soufan, a former longtime FBI agent who wrote a report in May for the Department of Homeland Security that warned, “To date, the United States has no national strategy to counter foreign influence.”

A senior administration official said there is a strategy but it is classified, adding, “The U.S. government has made significant progress in recognizing malign foreign influence operations and defending our homeland and our allies against this threat.”

Other experts decried the lack of a public national strategy and said that relative silence from the government — as well as President Trump’s years-long effort to discredit U.S. investigations of Russian interference, which he has repeatedly called a “hoax” — has undermined security agencies’ ability to educate the public about the threat and dissuade adversaries.

Democratic campaign officials said they were stunned to learn from media reports that their candidates had been potentially affected and wondered why they had not been briefed by Facebook or law enforcement. 

One official, who like other campaign representatives spoke on the condition of anonymity to discuss sensitive security concerns, argued that Facebook in particular had failed to “equip candidates with information to confront this threat yet again.” The posts were especially difficult to detect because they amplified existing viral content that had originated with domestic U.S. users.

“Democrats have to band together and apply pressure on Facebook, but in the end we need to plan for worst-case scenarios where we are fighting mass disinformation campaigns on our own,” said a digital director for one Democratic presidential campaign.

The Democratic National Committee, which released no public statement about the influence campaigns, “could be doing more to publicly lead this fight,” the digital director said, while acknowledging that the party was constrained in its ability to defend individual candidates because of allegations of bias that roiled the 2016 primary. 

A DNC spokesman laid responsibility at the feet of Facebook and the government, saying, “This is a time of crisis in our country, when the government should be stepping up.”

Asked about criticism from Democrats, Facebook pointed to an earlier statement saying that it had “shared information with industry partners, policy makers and law enforcement.” The company has sought in recent months to show that it has beefed up its anti-interference efforts since 2016, with chief executive Mark Zuckerberg telling lawmakers last week that Facebook’s defenses against disinformation are more “sophisticated than any other company has at this point, and frankly, governments, too.”

Individual Democratic campaigns, still competing against one another, have strained to arm themselves against viral disinformation. They receive briefings from the DNC, which uses software tools to detect trending topics that could be damaging to the party’s candidates.

The Biden campaign has entertained the idea of bolstering its defenses, at one point holding discussions with analysts at Flashpoint, a business risk intelligence firm. But the talks did not yield a formal contract, according to Tom Hofmann, the company’s vice president of intelligence.

Sen. Mark R. Warner (D-Va.), vice chairman of the Senate Intelligence Committee, called it “extraordinarily disturbing” that Facebook did not inform the Democratic campaigns before disclosing that they had been targeted. The decision, Democrats warned, could further erode the party’s trust that the company will provide the tools needed to respond in real time to escalating information warfare.

Facebook’s announcement last week underscored the evolving nature of the threat to campaigns. Although a minority of the Russian posts had explicit election-related content, many of the accounts set their location to swing states that could tip the 2020 contest, according to Graphika, a social media analysis firm that examined the operation for Facebook.

The company revealed that it had removed a network of accounts originating in Russia and targeting the United States, along with three networks of accounts originating in Iran that took aim at the United States and other countries, including several in North Africa and Latin America. The material offered a snapshot of the increasingly visual nature of foreign-backed disinformation, which games Instagram’s algorithm to serve users content on trending topics, analysts said. “GIFs, short videos, memes — that’s the stuff that’s doing really well on social media at the moment,” said Lisa-Maria Neudert, a researcher with Oxford’s Computational Propaganda Research Project.

The announcement came as foreign intervention in U.S. politics remains a heated partisan issue. Trump faces an impeachment inquiry over allegations that he withheld aid from Ukraine in return for that country promising to investigate his political opponents.

There have been clandestine efforts to thwart Russian and other influence, including a Cyber Command operation last fall to knock out Internet access to Russian trolls seeking to use U.S. social media platforms.

In July, shortly before stepping down as director of national intelligence, Daniel Coats created a new executive position on election threats and tapped a veteran intelligence official, Shelby Pierson, to hold it. She convenes regular meetings of all intelligence agencies collecting information on foreign threats, as well as entities that address election security. And an interagency working group, composed of many of the same agencies, has been coordinating responses to foreign influence.

“The threats are ongoing and persistent,” said a senior intelligence official, speaking on the condition of anonymity under ground rules set by the official’s agency. “They’re more diverse. We have more actors on the field. In addition to Russia, there’s China, Iran, hacktivists, ransomware.”

At a recent Silicon Valley meeting with tech firms, Pierson pressed the private companies to share more of what they were seeing with the government. Some tech executives replied that they were constrained by privacy laws.

The FBI and the Department of Homeland Security each have a foreign influence task force, with the FBI probing foreign threats to the United States generally and DHS emphasizing election systems. The FBI and other agencies offered group threat briefings to the presidential campaigns in May.

“There’s no law that requires us” to notify any individual of a potential foreign influence effort, said a senior FBI official, speaking on the condition of anonymity to discuss a sensitive matter. But such notification — especially to the tech platforms — has happened after consultation with other intelligence agencies to determine whether it can be done without compromising sources and methods, the official said.

In general, the official said, the FBI is not monitoring the Internet for misleading content, such as “deepfake” videos. “We are not the truth police,” the official said.

Experts say the relative silence from the White House, as well as Trump’s posture toward Russian interference, undercuts U.S. efforts and emboldens Moscow.

“The president’s continued questioning of the intelligence community’s findings about the 2016 election and the threat that Russia poses to U.S. national security undermines the deterrent effect of much of what the government is trying to do,” said Andrea-Kendall Taylor, a former senior intelligence officer on Russia at the National Intelligence Council and the CIA who is now with the Center for a New American Security.

In fact, Russian President Vladi­mir Putin appears unfazed by the U.S. response, joking in a public appearance this month about the prospect of interfering in the 2020 U.S. election. “I’ll tell you a secret: Yes, we’ll definitely do it,” he told a Moscow audience, cupping the microphone conspiratorially. “Just don’t tell anyone,” he added.

The metastasizing power of Russia’s influence operations was apparent in the days after Facebook’s announcement that it was taking down the accounts, as the material removed from Instagram continued to live on Facebook’s main social media service in the form of reposted content. 

A post from an account that posed as a black voter in Michigan still existed on a Facebook page with more than 30,000 followers called “The Black Truth and Nothing but the Truth.” When contacted by a reporter Wednesday, a representative for the page replied, “Thank you!” and said the material would be removed.

Following Facebook’s disclosure, Google said it removed a “small number” of accounts across its services, including some on YouTube, that were linked to Iran. Twitter said it received intelligence from Facebook and had not found similar behavior, but researchers pointed to Twitter accounts that appeared to have some links to the Iranian accounts removed by Facebook. 

Experts warned that simply removing fake accounts from the platforms would not deter hostile actors. After recent takedowns in Eastern Europe, Russians resorted to bribing authentic users to relinquish control of their accounts, according to Jakub Kalenský, a senior fellow at the Atlantic Council’s Digital Forensic Research Lab. 

Trump delivered no statement last week rebuking the apparent new Russian effort targeting his potential 2020 rivals, an operation that Facebook said showed “some links” to the Internet Research Agency, the St. Petersburg company and “troll farm” owned by an ally of Russia’s president.

Meanwhile, Trump’s allies in Congress have stymied election security bills that, among other steps, would compel American retaliation against the Kremlin for interfering in U.S. elections. One measure that passed the House on Wednesday seeks to close loopholes related to online political advertisements. But Senate Majority Leader Mitch McConnell (R-Ky.) has blocked its advance, saying in a speech Wednesday that it “will not do anything to stop malign foreign actors.”