Translation:Well, I don't know.
I think you should be careful using 知らない or any negative form of 知る, because when used in an improper context is actually very rude. わかりません is much safer when saying "I don't know". The former can be construed as "I don't care enough to know or tell you".
I totally agree! When I first read that I was like 'Woah, watch that attitude bro!'
If someone asks for gossip about someone else, would it appropriate to use「知りません」 to convey that you are not happy about gossiping.
I agree with SoitDX さん. But please be aware that if you are asked something about other's business (like "Do you have any idea where my wallet is?"), replying 知りません can be impolite because this may imply "I don't care." In such circumstance using "わかりません" for "I don't know." will be more proper.
しりません comes from しります meaning to know. わかりません comes from わかります meaning to understand. So it's like to say "I don't know" and "I don't understand" even though I've seen them used like having the same meaning, so it's kind of the same which one you choose.