Symantec NetDetect. NDETECT is part of Norton’s LiveUpdate. It checks whether you have an Internet connection and whether it can communicate with the Symantec website. If it can, it then switches over to LiveUpdate which itself checks for updates to your Norton AntiVirus, PCAnywhere, Internet Security, or Personal Firewall software.
If you see NDETECT in your Task List, it is only because you brought up the Task List at the exact moment that NDETECT was checking for an Internet connection. NDETECT only stays in the Task List very briefly. Also, NDETECT will only run if you have configured LiveUpdate to update your PC automatically, as it is run through Scheduled Tasks.
Quoted from this site:
(scroll down till you see ndetect)