A burglary prevention device is used with an existing door having an existing door knob lock and includes a door knob cover including a base suitably sized and shaped to fit over the existing door knob lock, a fastener attached to the base and extending outwardly therefrom, and a flexible chain connected to the fastener and engaged with a bottom edge of the existing door. In this manner, the chain is located exterior of the base. Advantageously, the door knob cover is capable of fitting over the existing door knob lock in such a manner that access is prohibited to the existing door knob lock.