Confidentiality in employer/employee relations - defaults in US law?

Question

I may soon be employed by a US company (I've never worked for one before). My question regards confidentiality of information in the employer-employee relations, by default (= by law/legal precedent), when this issue is not explicitly addressed in an employment contract.

Which party is required to keep the confidentiality of what kinds of information/knowledge?

1. The fact that you're employed at the company
2. The employment conditions
3. General, supposedly non-sensitive information about the company, e.g. how many employees it has, or how big its offices are, or what the cafeteria serves for lunch.
4. Technologies the company uses, in the general sense (e.g. we host our own cluster rather than renting virtual machines on the cloud)
5. More potentially-sensitive information, but one the disclosure of which does not in itself cause any damage, e.g. names of clients (when it's not a private/delicate matter), technologies used and so on.

I'm pretty sure the employee is required to keep 5 confidential, and isn't required to keep 1 or 2 in confidence. But what about the employer? Can it disclose that information? And what about the other categories?

Answer 1

As far as I know, by "default" the employer and employee are both free under the law to make any of these disclosures. I don't think there are any restrictions.

However, most US states provide for at-will employment, where employees may be fired at any time for any reason or no reason (other than specific exceptions like illegal discrimination). So if there is no contract, it would be perfectly legal for an employee to make any of these disclosures, but it would also be perfectly legal for the employer to fire them if they didn't like it. That applies even if the employee was never even told not to make such disclosures.