@Jianping Gu, I’m not sure what you are asking in your question, because hostile takeover of a business doesn’t necessarily equate to loss of IP as IP rights like patents and trade marks are legal rights. So even if there is a hostile takeover of a business, you’d still need to go through the process of assigning IP rights owned by the target to the acquiring entity, and this can get messy in a hostile situation. In the case of IP rights that are registered with the IP offices of certain countries, you’d need to work with IP agents/professionals to record the change in IP ownership. For unregistrable IP such as trade secrets and copyright (in most countries), this is done contractually. I guess if your plan is to prevent hostile takeover, then you either refuse to cooperate with the assignments, or find a way to make the IP redundant (which would be a waste). Hope this helps.
I’m certainly not an expert on this topic but there may be a few things that a company can do:
1. File for patents to protect their IP.
2. Limit trade secrets disclosure to only a select few people.
3. Or…if it is indeed a hostile take-over there is always the attempt to prevent the takeover by employing a poison pill