It's the most significant breach that Russian hackers have been able to pull off in an attempt to influence the 2016 U.S. presidential election. The Senate Intelligence Committee is currently hearing testimony from U.S. officials and members of President Trump's administration confirms that Russians tried meddling in the outcome.

More proof Russian hacking was involved in 2016 U.S. election

The Hill reports that Jeanette Manfra, an official with the Department of Homeland Security who works in the cyber-security and communications department, testified on Wednesday before the Senate Intelligence Committee that there's evidence that 21 states were targeted in the Russian hacking.

Those working for the Russian government were able to tamper with election-related systems. Manfra didn't elaborate on which states were targeted by the hackers over reasons of confidentiality. She disclosed that all of the states that were involved are aware of the breach.

There's already been confirmation that Arizona and Illinois had voter data breached by the Russians. Bloomberg released a report recently citing classified documents from The Intercept alleging that dozens of state were affected by Russian hackers. It's unknown if the Russians were able to successfully hack into other state's systems, but other officials testify that what they know so far, no voter tallies were influenced.

Bill Priestap, the assistant director of FBI’s counterintelligence division, stated that the Russians have tried for years to interfere with U.S. elections, but they went the furthest in 2016. The internet is making it easier than ever before to spread their message -- some of which included the crafting of "fake news" to sway votes from Hillary Clinton to Donald Trump.

Testimony from Samuel Liles, an official with the Department of Homeland Security also confirmed that voter ballots weren’t affected in the Russian meddling. He said the hackers were mostly “scanning for vulnerabilities” in the election much like someone who's walking by houses to see who's inside them. Liles added that the hackers managed to exploit a "small number" of systems.

In describing the severity of that, he likened it to a stranger being able to get through a house's front door.

Obama administration knew about hacking

Former Department of Homeland Security Secretary Jeh Johnson House informed the committee on Tuesday that the Obama administration was well aware of Russian hacking long before the election,but many would've criticized them for "taking sides." Moreover, Johnson implied that Trump was already ranting that the election system was rigged, and an announcement would've further undermined the election process in the eye of the American people.