According to canto 33 what souls are punished in the 9th circle? what sins have they committed

The souls of the Traitors and Benefactors are found in the 9th circle of Hell.
Three souls are prominent there for their Traitorous acts "Each of Lucifer’s mouths holds a sinner—the three greatest sinners of human history, all Traitors to a Benefactor. In the center mouth dangles Judas Iscariot, who betrayed Christ. In the left and right mouths hang Brutus and Cassius, who murdered Julius Caesar in the Roman Senate. Brutus and Cassius appear with their heads out, but Judas is lodged headfirst; only his twitching legs protrude. The mouths chew their victims, constantly tearing the traitors to pieces but never killing them. Virgil tells Dante that they have now seen all of Hell and must leave at once."