Symantec Defender

From Symantec: Symantec's Defender provides two-factor authentication which uniquely authenticates users without forcing them to remember another new password. For enterprises needing highly scalable user authentication in dial-up, VPN, firewall, or other remote access environments supporting RADIUS, Defender is a standards-based, strong two-factor authentication security solution.

Defender uses standards-based challenge/response technology to create a one-time password that is far more secure than static passwords. Its easy-to-use tokens compute this one-time password when challenged by the Defender Security Server. Then, without the authorized user's unique token and PIN to activate the token, potential intruders cannot compute the one-time password. Even if the password is captured, it doesn't pose a threat because the password is never valid again.