RJ11 to SD card?

This seems like such a simple question but I just cant figure it out. Is it possible to use the Arduino to take in a video from a serial connection and store it on a SD card or any other type of storage device for that matter?

I have a small home security camera that hooks up via RJ11 plug and I know that can be converted to a serial plug like db 9 or db 25 no problem. All I am looking to do is store as much video as possible and view it later. I don't need a wifi feed or motion sensors or anything like that. I have been reading a little about SD data loggers but I am not sure if that would still work for video, serial or not. Any input or advice is greatly appreciated.

Thanks.

You need to know what sort of signaling is being used on the serial connection, how the data is encoded, and what format you need to save it as. If it is RS232, do you get anything useful if you connect the camera to an RS232 port on a PC and just send the received byte stream directly to a file?