I started to have notification pop-ups called NDTV since a week ago and I can't find a way to remove it. I certainly didn't install a 'NDTV' app and I checked it is not in the application directory. I also used the AppCleaner to search for it but there is nothing. So how can I keep getting those notifications? They are really annoying and suspicious and I really need to get them off my system.
NDTV is New Delhi Television. Likely what you are seeing is push notifications from the website.
This page discusses Mavericks but the premise in Yosemite is the same:
To receive alerts for technology news, visit http://gadgets.ndtv.com using Safari, and click on the 'Allow' button when prompted with a message "The website "NDTV Gadgets" would like to send you push notifications in Notification Center."
Just like other OS X notifications, you can also tweak the alert style and choose between Banners and Alerts notifications and select whether you wish to receive notifications on your lock screen and the number of recent items in the Notification Center through the Notifications settings pane in the System Preferences of your Mac. You can also disable the notifications through these Settings.
I tested and the process worked exactly as they state it does. I was able to remove the notifications through System Preferences > Notifications.
(I didn't leave it turned on long enough to receive a notification...but do they do not reference breaking news?)