Required software development freelancer for Internet Security Tester job

We are developing a CRM as a web application. We would like to have it tested by an internet security specialist to make sure that it cannot be hacked or it's difficult to hack. We need a thorough initial testing and possible long term relationship to test this every now and then and after every update. Need an experienced specialist who could try to run software to attack the website and see if it can be broken into. The site is almost done, probably another week or two so before the test could be performed. It would also be great to hear some tips on how to improve internet security and resilience.

Skills & Expertise Required

software development