WASHINGTON — A loose network of conservative operatives allied with the White House is pursuing what they say will be an aggressive operation to discredit news organizations deemed hostile to President Trump by publicizing damaging information about journalists.

It is the latest step in a long-running effort by Mr. Trump and his allies to undercut the influence of legitimate news reporting. Four people familiar with the operation described how it works, asserting that it has compiled dossiers of potentially embarrassing social media posts and other public statements by hundreds of people who work at some of the country’s most prominent news organizations.

The group has already released information about journalists at CNN, The Washington Post and The New York Times — three outlets that have aggressively investigated Mr. Trump — in response to reporting or commentary that the White House’s allies consider unfair to Mr. Trump and his team or harmful to his re-election prospects.

Operatives have closely examined more than a decade’s worth of public posts and statements by journalists, the people familiar with the operation said. Only a fraction of what the network claims to have uncovered has been made public, the people said, with more to be disclosed as the 2020 election heats up. The research is said to extend to members of journalists’ families who are active in politics, as well as liberal activists and other political opponents of the president.