The malware in a file broken up by bit torrent is always located in the first piece. (which is rarely the first piece that is downloaded. The pieces are chosen at random and by availability). When that piece is scanned, the malware is detected before it ever gets a chance to try to execute in the full file. If that piece is quarantined or deleted, the full file will not even run. Actually the download will usually be halted at that point and never finish in the first place. Believe me, I know this is how it works from personal experience