Authenticating a user online, without compromising the user comfort is an important issue. The most popular approach to authenticate a user online is Password-based authentication. Studies show that, users (always) choose very simple passwords which are often easy to guess. On the contrary, randomly generated strings are difficult to remember, especially if the user is having many passwords. In this paper we present a dynamic password scheme based on patterns, called PassPattern System (PPS), which works using the existing infrastructure. PPS is an Adaptive Authentication System, where the strength of the system can be changed depending on the need of the application without compromising the user comfort. © 2008 Springer-Verlag Berlin Heidelberg.