As we know, most games of Paradox provides a very flexible and powerful mod ability.But, if some bad guy use it in an evil way.They can make a virus/spyware mod or even turn your machine into a bitcoin miner(by using mod as an entrance, then download the mining software running in background.And then, profit! ).Anyway, it's important to make sure you only use mod from reliable source. (same as any software you download from internet.)