Security software is designed to protect your computer, but sometimes it is overzealous. It may identify the data stream from TurboTax as suspicious and block the connection, resulting in the TT403 error.
Some users report that the error occurs specifically when trying to e-file their state return. This can happen if there is a mismatch in the data integrity between the federal and state forms during the transmission process. turbo tax error code tt403
Since the primary cause is file corruption, the most effective solution is to restore a backup of your tax data. Security software is designed to protect your computer,