Re: Router hijacked?
I assume your router was either provided by the ISP or, undoubtedly connects to a modem or other device provided by your ISP.
DNS hijacking or DNS redirection is the practice of redirecting the resolution of Domain Name System (DNS) names to other DNS servers. This is done for malicious purposes such as phishing; for self-serving purposes by Internet service providers (ISPs) to direct users' HTTP traffic via the ISP's own webservers where advertisements are served, statistics can be collected, or other purposes of the ISP;
and by DNS service providers to block access to selected domains as a form of censorship.
Do you ever click Home and instead of finding Google, Ubuntuforums, etc. you see a greeting or sign-in page from your ISP? That's a common form of DNS hijack. Even if the feature is not currently used by your ISP, the feature appears to be built in and not quite configured correctly.
"Oh, Ubuntu, you are my favorite Linux-based operating system" --Dr. Sheldon Cooper, Ph.D.