There's an old saying: "On the internet, no one knows you're a dog." They also don't know if you're a Russian propagandist disrupting the U.S. presidential election with hateful advertising. A new bipartisan bill introduced Thursday aims to change that.

The bill comes after Facebook, Google, and Twitter disclosed examples of political advertising bought on their platforms by Russian operatives seeking to sow fractious messages that pumped fake news and stoked racial hatred during the 2016 presidential election.

Under the "Honest Ads Act" introduced Thursday afternoon by senators Amy Klobuchar, Mark Warner, and John McCain, all digital platforms would be required to disclose information about who paid for political ads on their platform and try to prevent foreign actors from buying the ads.

"In the wake of Russia's attack on our election," said Senator Klobuchar at a press conference introducing the bill, "it's important to strengthen our defenses." She said laws had not kept pace with technology, allowing foreign nationals to exploit "loopholes" in order to "influence millions of American voters with impunity."

"These companies rely on the trust of all of us who use the platforms," said Senator Warner. "In light of what we've seen, it's time to take a step back."

Radio, TV, and newspaper ads carry rigorous restrictions around political ad disclosures. You can thank them for things like the awkward "I'm so and so and I approve this message" statements at the end of political TV ads.

But a 2006 carve out protected online advertising from those rules. The argument was that the internet is "a unique and evolving mode of mass communication" and requires fewer restraints than other forms of media.

The exemption had been sought and shaped by tech industry lobbyists. Facebook had argued that the ads on its platform were too small to fit the disclosure text.

The new act would require all digital platforms to keep a "public file" of the political ads sold on the site above a cumulative $500 per advertiser — and include a copy of the ad and a record of its performance and intended target audience.

Platforms would also be required to make "reasonable efforts" to keep foreign actors from buying political ads.

"The integrity of our elections is fundamental to democracy around the world," wrote Facebook CEO Mark Zuckerberg after the platform changed course and provided copies of the Russian-bought ads to Congressional investigators and announced new disclosure rules for political advertisers on the platform.

"We're going to bring Facebook to an even higher standard of transparency," he added.

Those self-regulatory initiatives weren't enough for lawmakers who have pushed for tighter controls.

The senators said this was a first step, light-touch action, targeted specifically towards purchasers of online political ads and wouldn't put restrictions on individuals' abilities to express themselves through, Klobuchar said, "cat videos...or cat videos about Donald Trump."

Other countries have moved more quickly to rein in internet companies selling political advertising. A week ago, U.K. Prime Minister Theresa May said her government was considering changing the legal status of Google and Facebook to regulate them as news organizations instead of tech companies. That would mean the two companies would each face fines if they allowed content deemed illegal to run on their sites.

Facebook's COO Sandberg argued in a recent interview that they're not a media company. "At our heart we're a tech company... we don't hire journalists," she said.

"I don't care what they call themselves, they're selling ads," said Klobuchar at the press conference.