How to protect and enforce trade secrets
I'd like to cover a few common issues that businesses face when it comes to trade secrets. One common example of trade secret information is the customer list. Most, if not all information on the customer list is something that people in your industry may already know. It's merely a list of customers or buyers. And the data itself may not be a trade secret. However, under the UTSA in California statute, the list itself is generally protectable if reasonable efforts have been made to maintain its secrecy. A competitor may attempt to determine who your customers are, but they may not appropriate a list of your customers from an employee or former employee.
Of course, if you put a list of your customers on your website, then the list would not be confidential. So, customers lists can be protectable if they're maintained as confidential information. But not when the company makes the list known. What about an employee who leaves a company with a brain full of things that one might consider the company's trade secrets?
Source: https://www.linkedin.com/learning/understanding-trade-secrets-a-deeper-dive/how-to-protect-and-enforce-trade-secrets