The way to get this information is to signal interest. What they're trying to prevent is you just getting the name of the company and then you going around them and applying directly. Honestly, the name of the company doesn't matter while you're in the pre-screening stage. Ask questions like, "what is the environment like? Is it a large company? Who will I be reporting to? Is it just dev or are there other roles I'll need to fill?" Eventually you'll satisfy their prescreening and they'll open up.