Security researchers have disrupted the botnet known as Pushdo, a coup that over the past 48 hours has almost completely choked the torrent of junkmail from the once-prolific spam network.Researchers from the security inteligence firm LastLine said that they identified a total of 30 servers used as Pushdo command and control channels and managed to get the plug pulled on 20 of them. As a result, the torrent of junkmail spewing from it dropped to almost zero on Thursday, according to figures from M86 Security Labs.