Anthony Ferrante coordinated the U.S. government’s response to Russian election interference. Now he’s helping a news site defend itself from a Russian billionaire’s lawsuit. For the last six months, a team led by a former top FBI and White House cybersecurity official has been traveling the globe on a secret mission to verify parts of the Trump dossier, according to four sources familiar with different aspects of the ongoing probe. Their client: BuzzFeed, the news organization that first published the dossier on U.S. President Donald Trump’s alleged ties to Russia, which is now being sued over its explosive allegations. The...