Which ports should security professionals scan when doing a test?

What will be an ideal response?

As a security tester, you need to know which ports attackers are going after so those ports can be closed or protected. Security professionals must scan all ports when doing a test, not just the well-known ports Many computer programs use port numbers outside the range of well-known ports. For example, pcAnywhere operates on ports 65301, 22, 5631, and 5632. A hacker who discovers that port 65301 is open might want to check the information at the Common Vulnerabilities and Exposures Website for a possible vulnerability in pcAnywhere. After a hacker discovers an open service, finding a vulnerability or exploit isn't difficult.