Security is a major issue in developing software systems. It
is widely recognized that security aspects must be considered in all the
phases of the development process from the analysis of the organizational
context to the nal implementation of the software system. However,
current approaches for designing secure systems only target particular
security aspects at specic stages of the development process. A unied
process combining these dierent approaches is still missing. This paper
surveys several existing techniques and discuss the need of a general
framework for integrating them into a single development process.