Peer-to-peer file sharing programs have the potential to expose everything saved on a computer. Feinman recommends configuring all peer-to-peer file sharing programs to disable the sharing of personal folders so identity thieves can't download tax returns.

Feinman said file sharing is likely the most dangerous and detrimental error that can be made during tax season. Peer-to-peer tools let potential thieves search for keywords which, if files aren't protected, could allow them to download a tax return.