The attack on a computer system with the intention of finding security weaknesses are becoming increasingly frequent and evermore sophisticated, potentially gaining access to it, its functionality and data. Organizations wishing to ensure security of their systems may look towards adopting appropriate tests to protect themselves against potential security breaches. One such test is to hire the services of penetration testers (or “pen-tester”) to find vulnerabilities present in the case study for “Cairo Cleaning and Beautification Agency”, and provide recommendations as to how best to mitigate such risks. By using series of the standards built on the application of data mining methods specifically decision tress model, Logistic regression, association rules model, Bayesian network for making reference penetration testers. This paper discusses the definition and role of the modern pen-tester and summaries current standards and professional qualifications. The paper further identifies issues arising from pen-testers; their motivation is to improve security.