"Last Week Tonight” host John Oliver asked viewers to submit comments to the FCC on net neutrality rules. (Eric Liebowitz)

Update: FCC spokesman Mark Wigfield said late Monday that the Federal Communications Commission has updated its systems to a cloud service that should be more resilient against attacks. He affirmed that there had been a cyberattack on the agency's site Sunday, and said that the agency also suffered an attack in 2014 after Oliver's previous segment.

Original post: The Federal Communications Commission said Monday that its website was the target of an attack designed to overwhelm it with traffic and keep people from commenting on its proposals. The attack prevented the FCC from responding to people attempting to submit comments since Sunday night, the agency said.

Before the FCC revealed the cyberattack, some had linked comedian John Oliver to the agency's website problems, which appeared to begin after the “Last Week Tonight” host asked viewers to submit online comments to the FCC to save its current net neutrality rules. Since Oliver's show aired on Sunday, the commenting site has had intermittent connectivity problems.

The FCC said in a statement, however, that its investigation shows the site's problems were caused by a cyberattack, not by an influx of people trying to file comments.

A federal court recently ruled that high-speed internet is a utility, not a luxury. The Washington Post's Brian Fung explains why net neutrality matters to consumers. (Whitney Leaming/The Washington Post)

“These actors were not attempting to file comments themselves; rather they made it difficult for legitimate commenters to access and file with the FCC,” said David Bray, the agency's chief information officer.

But the agency's statement has raised skepticism from consumer advocacy group Fight for the Future. The group said in a statement that it finds the timing of the attack too coincidental. The group raised questions about whether the FCC was diagnosing the slowdown correctly, or whether an outside attack could have been launched specifically to keep Oliver's viewers from commenting.

“The FCC should immediately release its logs to an independent security analyst or major news outlet to verify exactly what happened last night,” said the group's campaign director, Evan Greer.

On Sunday, Oliver criticized FCC Chairman Ajit Pai's draft proposal to undo Obama-era rules that forced Internet providers to behave more like traditional telephone companies — and made it illegal for them to block or slow websites. The TV host asked people to visit gofccyourself.com, which offers a link to the FCC's comments section. Oliver also poked quite a bit of fun at the chairman himself (including a gag making fun of Pai's well-documented affinity for an oversize mug featuring the logo of Reese's Peanut Butter Cups).

Pai has argued that there is no indication that Internet service providers planned to make the Web less open or free. He characterizes the current net neutrality rules, which he voted against as an FCC commissioner, as governmental overreach.

This weekend's episode is a repeat effort in support of net neutrality regulations on Oliver's part. The TV host asked his viewers in 2014 to comment on the FCC's website about net neutrality as the agency mulled its options. The site crashed shortly thereafter, apparently from the influx of commenters reaching out to then-Chairman Tom Wheeler asking him to protect the principle of a free and open Internet.

That episode has been called a turning point for the net neutrality movement. Advocates hope that Sunday's segment will do the same.

“In 2014, John Oliver’s net neutrality segment was one of many inflection points in the public campaign to secure strong rules,” said David Segal, executive director of the advocacy group Demand Progress. “In his segment last night, Oliver exposed the hypocrisies and spin of Chairman Pai and the large ISPs, who continue to make Orwellian claims that they support the open Internet while doing all they can to dismantle the legal foundation necessary for strong net neutrality rules.”

The FCC site has received tens of thousands of comments since Sunday's episode aired.

Pai has moved quickly to enact a more limited, conservative approach to the agency's actions in his first 100 days as chairman. He has introduced a proposal to roll back Wheeler's rules. The FCC is scheduled to vote on that proposal May 18.