I posted a couple of days ago about a free DNS checker to see if your ISP’s name servers are vulnerable to the DNS poisoning exploit that is now in the wild. I found another reputable one: https://www.dns-oarc.net/oarc/services/dnsentropy. Or at least, it seems reputable. This one has a more elaborate test than the one provided in my previous post.
Another DNS Checker: Is Your ISP Vulnerable to the DNS Poisoning Exploit?