Auditing / external evaluation

Third-party evaluation of your cybersecurity is very useful

Getting an independent third-party to evaluate your cybersecurity practices is very useful (and can provide reassurance to clients who inquire about your capabilities).

More advanced protection would mean developing an annual audit/assessment plan including a regular (quarterly?) vulnerability scanning process. Once you have achieved what you believe to be an adequate level of cybersecurity you should do regular penetration testing.

For an explanation of those terms and to learn more see "The Difference Between a Vulnerability Assessment and a Penetration Test" https://danielmiessler.com/study/vulnerability-assessment-penetration-test/#gs.aJmU2vs