The eight men allegedly purported to be successful traders on the social media platforms and then engaged in a so-called "pump and dump" scheme by hyping particular stocks to their followers with the intent to dump them once prices had risen, according to prosecutors in the Southern District of Texas.

The U.S. Securities and Exchange Commission (SEC) said it has filed related civil charges against the defendants in the scheme, claiming that seven of the defendants used Twitter and Discord to boost stocks. It said the eighth was charged with aiding and abetting the scheme with his podcast.

"Securities fraud victimizes innocent investors and undermines the integrity of our public markets,” said Assistant Attorney General Kenneth Polite of the Justice Department's Criminal Division.

The individuals charged were Texas residents Edward Constantinescu, Perry Matlock, John Rybarczyk and Dan Knight, along with California residents Gary Deel and Tom Cooperman, Stefan Hrvatin of Miami and Mitchell Hennessey of Hoboken, New Jersey.

Matlock pleaded not guilty following his arrest on Tuesday, according to a court filing. His attorney did not respond immediately to a request for comment.

Rybarczyk and Deel did not respond immediately to requests for comment. The others could not immediately be reached.