Intermittent DNS Hijack Found

Hi,

I’ve been running the Avast Free Antivirus Network Inspector, and it intermittently flags “DNS hijack found” and indicates the hacked domains are www.msftncsi.com and www.msftconnecttest.com.

I’ve checked my router settings, I set the DNS to Google’s public DNS, and every time I’ve checked since making that change, I haven’t noticed any changes to settings. I started running the network inspector multiple times, not making any changes between runs (or doing anything for that matter), and sometimes it’ll still flag a DNS hijack and sometimes it’ll say I’m secure. I’ve also been using the mobile version of Avast, and that keeps saying my WiFi is secure; it hasn’t indicated a DNS problem.

When I type a non-existent URL, the browser says that the site can’t be reached, which I’ve heard is a good sign.

Could this be a false positive? If so, how could I be sure? Or, what could be triggering this DNS hijack flag?

Thank you.