A former Democratic congressional aide who doxxed Republican senators during a confirmation hearing for Supreme Court Justice Brett Kavanaugh will be sentenced to prison Wednesday.

Former computer administrator Jackson Cosko carried out what prosecutors said was the largest known data theft in Senate history and used it to blackmail a witness, to plot to extort a senator and to threaten others.

He left operational spy devices on the Senate network that went undetected by police even after he was arrested and his plot was discovered, prosecutors said.

Prosecutors are seeking to make an example of Cosko for criminally attacking people who disagreed with him politically, citing a rise in such incidents.

A former aide to Sen. Maggie Hassan and Rep. Sheila Jackson Lee is headed to prison Wednesday for what prosecutors said was the largest known data theft in Senate history.

The former aide, Jackson Cosko, pleaded guilty in April to crimes related to an unparalleled effort to ransack a Senate office, extorting a Democratic senator, illegally harming Republicans for their political views, and blackmailing a witness.

Prosecutors asked for nearly five years in prison for Cosko, a onetime congressional IT aide to Hassan. Cosko admitted he stole the New Hampshire Democrat’s data out of revenge for being fired, then used it to doxx Republicans during the Brett Kavanaugh hearings.

“The government believes that a significant sentence would help to make clear that difference of political opinion do not entitle people to engage in politically motivated, criminal attacks threatening elected officials with whom he disagrees, and would thereby encourage respect for the law, and deter future criminal conduct,” prosecutors wrote.

New details emerged in their sentencing memo that made the case of Cosko — the Bernie Sanders-supporting son of a millionaire San Francisco developer with ties to California Sen. Dianne Feinstein and House Speaker Nancy Pelosi — even more shocking.

A second Hassan staffer who was friends with Cosko served as his accomplice in exchange for rent money helped him physically break into the office at night and pilfer internal emails even after he was fired, prosecutors’ sentencing memo shows.

The Daily Caller News Foundation first reported that the accomplice, who has since been fired, is Samantha DeForest-Davis. Hassan’s office subsequently confirmed her identity, yet DeForest-Davis has not been charged with any crime.

Even after Cosko was arrested and a computer was quarantined, Capitol Police and Senate employees did not realize that keylogger devices were plugged in to many of the office’s computers, according to prosecutors. The devices continued to beam every keystroke — including passwords to personal and business accounts — over a WiFi signal that could be accessed from the public hallway.

The Senate later realized that it was still being spied on only because Cosko informed government agents of the devices, the memo says. Police still have been unable to detect the devices’s WiFi signals, making it impossible to rule out that they aren’t plugged in elsewhere in Congress.

Prosecutors say the case is emblematic of rising threats against political opponents

Prosecutors said Cosko had “self-righteous entitlement” and a “belief that he could violate the sanctity of the United States Senate at will and threaten individual Senators as he pleased.”

He wanted to use stolen data “to punish people who disagreed with his politics” by publishing the personal information of Republican Sens. Lindsey Graham, Orrin Hatch, Mike Lee, Rand Paul, and Mitch McConnell, the memo says, which noted that Cosko laughed about his actions.

Prosecutors said his case must be a deterrent to what they said are rising politically-motivated attacks.

“The defendant operated under the belief that he was entitled to inflict emotional distress upon United States Senators and their families, simply because they disagreed with the defendant and had different political views,” prosecutors wrote. “The government believes that there appears to have been an increase in similar criminal harassment, particularly through social media channels, by people across the political spectrum.”

In a sentencing memo, prosecutors described “a months-long series of burglaries and sophisticated data theft offenses directed at the office of United States Senator Maggie Hassan; to a separate set of ‘doxxing’ offenses through which he maliciously released personal information of Senators Lindsay Graham, Orrin Hatch, Mike Lee, Rand Paul, and Mitch McConnell; and to obstruction of justice, because he attempted to silence a witness by threatening to release the private health information of a Senator’s children, because he corrupted another person and persuaded her to attempt to ‘wipe down’ the scene of his burglaries, and because he attempted to destroy evidence in his own apartment.”

Prosecutors dismissed arguments by Cosko’s team of attorneys that drugs were behind the defendant’s behavior and that high-end counseling and treatment paid for by his parents could cure it. They said Cosko’s behavior was premeditated and deliberate and that he took pleasure in learning of Republicans’ pain.

Prosecutors said Cosko laughed “aha it ruined [Hatch’s] wifes birthday [sic].”

A vengeful employee

Hassan hired Cosko as an IT administrator “entrusted with access to all of the computer systems and data in the Senator’s office,” even though he had a prior criminal record, prosecutors said. In May 2018, he was “terminated for performance-related reasons” that Hassan has declined to explain. (RELATED: Hearing Reveals Congress Provided ‘No Supervision’ Of IT Aides, Missed Red Flags, But Members Block Proposed Reforms)

Prosecutors said he “continued to be angry about his termination for months” and took “advantage of his in-depth knowledge of the office’s computer security measures and practices, engaged in an extensive computer fraud and data theft scheme that he carried out by repeatedly burglarizing Senator Hassan’s Office.”

“The defendant ultimately copied entire network drives, sorted and organized sensitive data, and explored ways to use that data to his benefit,” they continued.

One of his aims was to extort Hassan’s office into giving him a positive job reference and finding out whether it had given him bad references, prosecutors said.

Regardless, Texas Democrat Jackson Lee hired him anyway, despite the criminal record and termination from Hassan’s office. The job was unpaid, a lifestyle apparently made possible by Cosko’s parents’ wealth. But it gave him access to the House computer network, which he used to continue his data theft and extortion.

“The defendant broke into Senator Hassan’s Office on at least four occasions, including on or about July 26, 2018, August 6, 2018, and October 2, 2018,” prosecutors said. “The defendant gained access to Senator Hassan’s Office by unlawfully obtaining keys from SUBJECT A, a staffer who was (at the time) employed in the Office.”

“The defendant obtained and took dozens of means of identification (including network login credentials) belonging to at least six employees of the Office of Senator Hassan – that is, his conduct constituted numerous instances of identity theft,” they continued. “The defendant also surreptitiously installed ‘keylogger’ devices on at least six computers in Senator Hassan’s Office,” which were “designed to be unobtrusive, legitimate looking devices that would go unnoticed by the individuals that were using the affected computers.”

The devices were “designed to record the keystrokes that Senate staffers typed on their Senate-owned computers – including the keystrokes that comprised usernames and passwords for Senate computers and computer networks, as well as personal e-mail accounts,” prosecutors said.

Then, during the confirmation hearings of now-Supreme Court Justice Brett Kavanaugh, Cosko used his House computer to post the stolen personal information of Republicans on the Senate Judiciary Committee to Wikipedia.

After Kentucky Republican Paul — who was the victim of a physical assault and has been shot at — demanded accountability for the mystery “doxxer,” Cosko targeted Paul and Senate Majority Leader Mitch McConnell “with the intent to intimidate them,” posting their personal addresses and phone numbers, knowing that others would use the information to harass them, prosecutors said.

On Oct. 2, Cosko went back to Hassan’s office for more after asking Deforest-Davis for her key. According to prosectors, he was caught in the act by a Hassan employee and fled, then emailed the witness: “If you tell anyone I will leak it all. Emails signal conversations gmails. Senators children’s health information and socials.”

Luke Rosiak is the author of the new book Obstruction of Justice: How the Deep State Risked National Security to Protect the Democrats , about a computer hack on the House of Representatives.

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