Applying for a patent can be a confusing process. There are many layers to the application process.
The U.S. Patent and Trademark Office explains you may run into a notice on your application that says referred by L&R for third-level security review. The review is a legal requirement for the USPTO. Officials have to send any applications for review if there is a determination they could be a risk to national security.
What it means
When you get the notice, it simply means a defense agency will look over your application. They will make a determination about the security risk. If they feel it could threaten national security, then they will issue a secrecy order. This means your patent becomes a secret that the USPTO will not publish or make public. You will receive a notice about the final determination.
The security review could take over six months. The USPTO does not have authority over the process. The review depends on the agency doing it. It might take quite a bit of time if the agency has a backlog.
Once you receive a secrecy order, you must comply with what it says. This may limit how you can finish filing and what you can do moving forward. It is important to read the order and make sure you understand it completely before moving ahead with the patent process.
Remember if you receive a security review notice, the USPTO will only have limited information to offer you. You will need to deal with the agency conducting the review if you have questions.