Who's This? That trio on page 8 of Who's Who's 9th volume.
How you could have heard of them: They're often seen sitting and drinking in the background at the Oblivion Bar, a setting used in the Shadowpact comics (among other places).
Example story: Comic Cavalcade #1 (1943), "Hitler Is a Bum!"
As you can see, these adventures don't take themselves too seriously. The Ghost Patrol's stories are full of these kinds of shenanigans, generally scaring wicked German and (sometimes) Japanese soldiers and leaders and causing accidents that save Ally lives. This isn't even the only time they've haunted Herr Hitler! Few of these stories have been reprinted, though the Archives series is starting to (Comic Cavalcade Archives, for example). Simple and fun propaganda comics worth checking out!
Who else? Might have gone for the Ghost, but the Charlton villain eventually made a DC appearance against his old/new foe Captain Atom. He WAS completely unknown when he appeared in Who's Who though. Likewise, the Global Guardians' appearances in Justice League books within a couple years makes me skip over them. But has anyone ever read a solo Golden Gladiator story? Me neither.