There are technical security patterns for web services. These detail how the code should be handled at each step of the way. For example: input validation, secure transaction mechanisms, capturing secure information.
“A security pattern is a well-understood solution to a recurring information security problem” (Elder, Kienzle, et. all). For example: user account lockout, third party access into your network etc.
Why Use Patterns?
Because they assist by already incorporating elements without you having to think about them. They are tools to be put into your toolbox.