Washington: People connected to the Russian government tried to hack election-related computer systems in 21 states, a Department of Homeland Security official testified Wednesday.

Samuel Liles, the Department of Homeland Security’s acting director of the Office of Intelligence and Analysis Cyber Division, said vote-tallying mechanisms were unaffected and that the hackers appeared to be scanning for vulnerabilities — which Liles likened to walking down the street and looking at homes to see who might be inside.

But hackers successfully exploited a “small number” of networks, Liles said, likening the act to making it through a home’s front door.

Liles was testifying before the Senate Intelligence Committee, which is investigating Russia’s efforts to meddle in the 2016 presidential election, and his remarks add some clarity to the breadth of the Kremlin’s cyber mischief. Officials in Arizona and Illinois had previously confirmed that hackers targeted their voter registration system, though news reports suggested the Russian effort was much broader.

Reports earlier this month said Russian hackers “hit” systems in 39 states, and the Intercept, citing a classified intelligence document, reported that Russian military intelligence “executed a cyberattack on at least one US voting software supplier and sent spear-phishing emails to more than 100 local election officials just days before last November’s presidential election.”

In a separate hearing before the House Intelligence Committee on Tuesday, former Department of Homeland Security secretary Jeh Johnson testified that Russia’s meddling, directed by President Vladimir Putin, was “unprecedented, the scale and the scope of what we saw them doing.” The testimony came a day after White House press secretary Sean Spicer said at a briefing he did not know whether President Donald Trump believes Russia interfered in the 2016 presidential election.

Officials also revealed what appeared to be a breakdown in communications about how severe the threat appeared, and they reported tensions the Obama administration faced in trying to publicly warn of meddling in the face of a sceptical then-candidate Trump.

“One of the candidates, as you’ll recall, was predicting that the election was going to be rigged in some way. And so we were concerned that, by making the statement, we might in and of itself be challenging the integrity of the — of the election process itself,” Johnson said.

The testimony came during a morning of double-barrelled intelligence committee hearings — one in the House and one in the Senate — that underscored the US intelligence community’s months-old determination that Russia attempted to meddle in the election. The issue has become a flashpoint for the Trump administration as congressional committees and a special counsel investigate the interference and whether the Trump campaign may have become enmeshed in it.

A day earlier, Trump spokesman Sean Spicer said he still has yet to know the president’s thoughts on whether Russia interfered.

Johnson said Russian hacking didn’t change election totals, but he can’t be sure other meddling didn’t influence public opinion.

“It is not for me to know to what extent the Russian hacks influenced public opinion and thereby influence the outcome of the election,” he said.

Senators said the Homeland Security Department should reveal which state election systems were targeted by hackers as Jeanette Manfra, the department’s undersecretary for cybersecurity, demurred.

Sen. Mark Warner of Virginia, the committee’s ranking Democrat, noted that the FBI has confirmed intrusions into voter registration databases in Arizona and Illinois, and said Americans need to know the identities of the other 19 states where meddling was detected.

“I do not believe our country is made safer by holding this information back from the American public,” he said. “To have the number of states that were hacked into or attempted to be hacked into still kept secret is just crazy in my mind.”

Manfra said the department was still tracking the meddling in the 21 states and believes it’s important to protect the confidentiality of the states.

State elections officials, who testified before the Senate committee, complained that DHS could have offered more information about the hacking.

In addition to scanning voting systems for vulnerabilities, Russian hackers acquired and engineered the release of emails from the Democratic National Committee and Hillary Clinton’s campaign chairman, John Podesta, according to US intelligence committees.

“In retrospect, it would have been easy for me to say I should have brought a sleeping bag and camped out in front of the DNC in the late summer,” Johnson testified. He said the severity of Russia’s efforts persuaded him to sign onto an October 7 statement publicly blaming the Kremlin for what had happened, even though doing so could have been perceived as “taking sides” or “challenging the integrity of the election itself.”

“My view is that we needed to do it, and we needed to do it well before the election to inform American voters of what we saw,” Johnson said. He added: “I think the larger issue is it did not get the public attention that it should have, because the same day the press was focused on the release of the Access Hollywood video.” That video showed Trump bragging about kissing and groping women.

Officials declined to say which 21 states were targeted or identify those that had data — such as voter registration lists — removed from their systems. Jeanette Manfra, the acting deputy undersecretary for cybersecurity and communications, said she could not do so because it was important to protect the confidentiality of those victimised.

FBI Assistant Director of Counterintelligence Bill Priestap testified Wednesday before the Senate Intelligence Committee that Russians also pushed false news reports and propaganda online, using amplifiers to spread their message. He said Russia for years has tried to influence US elections but that the “scale” and “aggressiveness” of its efforts in 2016 made the attempts more significant.

“The internet has allowed Russia to do so much more today than they’ve ever been able to do in the past,” Priestap said. He said Russia’s goal was to “sow discord” in the United States and to “denigrate” Clinton and help Trump.

Johnson suggested that in the aftermath of the hacking, the federal government should “encourage a uniform set of minimum standards for cybersecurity when it comes to state elections system and voter registration databases.”

But he acknowledged that doing so might be a heavy lift, given that state election officials are naturally suspicious of what he called a “federal takeover” of their election practices.

“State election officials are very sensitive about what they perceive to be federal intrusion into their process,” Johnson said, noting that he often encountered officials pushing back and arguing that “it’s our process, our responsibility.”