CCTV systems are often installed in and outside of homes to try and protect it and the occupants. It may be that the CCTV system is enough alone to deter criminals but if they do attempt to break in to your home, you will hopefully have some decent footage to pass on to the police who can then work on identifying the culprits and bringing them to justice.
Even though you may not think it, your CCTV system can also be a huge help to others on your street or in your area as it could pick up other people or vehicles that the police are searching for. For example, if someone has gone missing then it may be that your CCTV system picks them up walking past your house at a certain time. This can massively help the investigation and help the police plan the route the missing person has taken. For this reason, it is important to try and keep CCTV footage for as long as possible before recording over it. Try and have at least 3 months’ worth of CCTV footage at any one time as it is likely that it will be needed within this time scale if a situation should arise.