As a penetration tester, your job is to test the security of a network by attempting to hack into an application, system, or computer. Penetration testing can occur in a variety of ways, from physical interaction with the machine you’re trying to hack to attacks sent over the web. Aside from helping clients test for vulnerabilities, your job also includes explaining how you got in and providing recommendations for stopping others from repeating your actions. In some cases, you may be asked to help investigate cyber crimes or explain methods and techniques in criminal trials. Success in this job is often measured by how many security holes you find and close.