there's no such software... imagine if there would be? millions would have been hacked right now and the net will be flooded with complaints. Either you somehow shared your password to anyone or you were a victim of a key logger..but this happens mostly in internet shops..when a person sitting beside you or behind you somehow copied your log-in details...sometimes even shop owners placed secret cams around the shops for this purpose to hack big time online gamers...then they sell the accounts for the highest bidder.. A few years back, every time net surfers failed to log-out and shuts down the PC to beat the allotted time, the account is still logged-in when another user comes in and opens the PC..but this problem have already been fixed by Yahoo.