These are investigations for clearances. They ensure that the candidate doesn't have anything that can be exploited by a foreign government. The article mention

These are investigations for clearances. They ensure that the candidate doesn't have anything that can be exploited by a foreign government. The article mentioned this. Before you get a clearance you'll have to go through a very thorough background check. In the case of top secret information they'll dig into your entire life and even give you what's called a "full lifestyle polygraph", meaning no topic is off limits.