The IRS e-file system has never had a security breach.  In fact, over 400 million returns have been electronically filed since 1986 without a security incident.

FACTS

• The IRS e-file System is not done over e-mail
• The IRS e-file System has many built-in security features
• The IRS e-file System employs multiple firewalls
• The IRS e-file System uses state of the art virus and worm detection
• The IRS e-file System meets or exceeds all government security standards
• The IRS e-file System is constantly tested for weaknesses by penetration testing
• The IRS e-file System has never had a security breach 
• All Internet transmissions will use SSL (Secure Sockets Layer) encrypted security measures.

IRS e-file transmissions are very secure because the IRS has been extremely diligent in the design, development, analysis and testing of the current infrastructure and system.  IRS e-file meets or exceeds all government security standards and includes multiple firewalls.

Most e-filed online tax returns are transmitted over phone lines from the return preparer to a third-party transmitter. From there, the returns are forwarded over secured lines to the IRS.  Intercepting telephone transmissions is quite difficult and requires access to phone company major transmission lines.  Also, to transmit data like tax returns over telecommunications lines means that the information gets converted into digital format which could not be easily read even if it were intercepted.