I feel that this is definitely a hack of some sort and an interesting one.
I am using a Beetel 450TC1 ADSL2+ modem router and here is what I face:
* First, I disconnect the telephone line from the modem-router, reset it and then access it using the default user/password combination.
* I just change the admin password
Now as long as I do not connect my phone cable to the modem-router I can login to http:// 192.168.1.1 using the password that I setup. The moment I connect the phone cable and as soon as the Internet LED indicator glows up, I try logging into http:// 192.168.1.1 using the user/password combination that I setup and it fails. Even the default user/password combination does not work.
I repeated this multiple times. I conclude that as long as I do not connect my phone cable; thereby accessing my DSL or the internet, my modem-router password remains unchanged.
I found a similar post here by @whitespy9: Router admin password was changed, how did this happen and how to prevent
My question: Have you come across such a scenario? If so, what was your solution?