If the Media does know the name, and it was damaging to President Trump, then it would already have been leaked.
If the Media knew the name and it was damaging to the Democrats, they'd delay releasing the name as long as possible.
So it seems likely to me that the Media doesn't know the name yet...
Or the indictment doesn't relate directly to Trump colluding with Russians so they don't have to waste a source by leaking.
Manafort would be my guess. Law enforcement doesn't go on a no knock raid early in the morning for fishing expeditions. They must have had something on the guy that merited a search warrant.