When you say 'security system', do you mean CCTV, or an alarm system for break-ins?
If your talking CCTV, ZoneMinder is great! I believe it's free, too.
If you want simple webcam monitoring, you can use Yawcam.
Personally, I would go with ZoneMinder or a standalone DVR system. Please remember that the quality of your cameras is essential in actually identifying people or cars. Don't buy webcams and expect them to capture a clear picture of a burglar.
no sir actually i want when someone open a door start recording
&
i want to know how to controll stepper motor with my pc
stepper motor attach with web cam & so i can controll it any where in the world i can monitor at my home (with remote computing software- actually i have a idea for that)