Two of the key security issues are the authentication of requests and privacy. These issues boil down to one using mechanisms to ensure that I know who you say you are. These mechanisms are more important in some Web interactions than in others. The more complex Web interactions such as database transactions and shopping require the execution of programs on the server. These programs are most commonly used when you enter and submit data via a form.
Security is a major issue here.
This protocol controls how programs communicate with the Web server. CGI gateway programs can be written in any language that can execute on the server machine. Environment VariablesThe server puts information in special environment variables before starting the gateway program. The gateway program can then access these variables and obtain their contents. These three mechanisms specify data transfer from the Web server to the gateway program.