Greetings @deepak94,

In my opinion, moonlighting is not good because of some reasons like data theft or others as you mentioned, but along with that firing company employees are also not a good option, company has to make a plan or think about this problem

if they find that one employee is doing such work in two companies the company should allow him to work more in the same company for which the employee will get overtime (Extra money) or if extra work is not an option that company has to set guidelines for the employee for working in two companies together rather than firing him

I hope you got my point , Excellent read deepak