Ordinarily, good English avoids using two negatives in a sentence. I’m thinking of sentences such as these:
I ain’t got none.
It don’t make no never-mind.
But we do have a way to use two negatives, when it’s what we mean. I’d say it’s a kind of understatement. I ran into a nice example the other day:
Meanwhile, there’s little reason to think that stealthy, sophisticated hackers aren’t already exploiting BlueKeep in secret, says Jake Williams, a former NSA hacker and founder of the firm Rendition Infosec.
You can get away with a sentence like that if you want to sound “literary,” but when you’re into being clear and concise, something like this is better:
We think that sophisticated hackers are already exploiting BlueKeep in secret.
Not as colorful, perhaps, but more to the point. And that’s what you want, isn’t it?