How can I get the Virus's arp to sound like this?

Well, the pattern is obviously all 16ths, the order is up&down, and the range should be 4 octaves. Press down chords in 3 or 4 notes, and if I heard correctly, the chord changes when the "up" turns into "down", so when that happens, make sure your hands don't completely leave the keyboard because that will make the arp re-start with "up".
Good luck!