I have a CCTV DVR installed by a local security company and I have been meaning to try this in order to secure the DVR. I think the company had access to it via the cloud app. Your question prompted me to try to get into its admin console, and here is what I have been able to do so far.
I couldn't telnet to it, however, using a web browser (I had to use Internet Explorer because Chrome and Firefox did not allow required plugins to load, although I am sure there must be a way to use these) I could get to its web admin console.
Search for your model number and default admin user name and password (unless of course you already know the credentials). I got into mine in less than a minute and changed its admin password and set a static IP address. There are a number of settings in the web admin console, although I could not find any to enable Telnet or SSH. At least now I know the installing company cannot get into the system - the cloud app on my phone stopped working and I had to enter the new password into the app).
I connected a USB mouse and keyboard, along with an old VGA monitor to the DVR and was able to access its console although, as yet, I have not been able to do much with it apart from view the various camera feeds.
I'll explore it further later.
Out of curiosity, what are you trying to achieve by using telnet to access the DVR?
Edited by teshy (Mon 28-Jan-19 16:43:30)