One time password is one of the most common forms of 2 factor authentication (2FA) in the world, because it provides a level of security that's unmatched by any other technology. With OTP, a unique password is specifically generated for each connection attempt, by special software, and used as part of the login process. Some OTP products generate the unique password automatically every minute and others generate it upon request. The OTP cannot be re-used to connect again, so it cannot be stolen, and there's no use for brute-force guessing, because the OTP will expire before the guess engine can go through more than a few hundred password variations.
The most well-known provider for OTP solutions is RSA (the company, not the algorithm, although the RSA company was named after its founders Ron Rivest, Adi Shamir, and Len Adleman, who also developed the algorithm RSA). RSA's OTP solution uses a piece of software that generates a new PIN every minute. You can run the software...