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Where is the security key on a comcast modem located? The security key on a Comcast Modem is located next to the serial  number of the unit. Sometimes the serial number is the number used  as a security code if it is not printeâ¦d on the device. (MORE) 1 person found this useful.
Views Â· Most Viewed Writer in. Wi-Fi with 270+ answers. If you are using one of the standard Comcast Modem/Router combos, you need to log into it with a web browser at http://10.0.0.1 with a username of admin and a password of password. From there, find the Wi-Fi section, and change the Wi-Fi password. More details: Securing Your Wireless Gateway Network.