With a properly installed wired system, it is very difficult. The cameras and recorder sit on your local network, footage is stored on-site rather than in the cloud, and all remote connections are encrypted. There is no cloud server holding your data that an attacker could target.
Most CCTV hacking stories involve cheap IP cameras with default passwords, no encryption, and open ports exposed to the internet. These cameras are often found by automated scanners and accessed by anyone who tries the factory login. A professionally installed system avoids all of this.
Doberman installs UniFi Protect systems where the cameras communicate only with your local NVR over Ethernet. The cameras are not individually accessible from the internet. Remote access goes through an encrypted tunnel to the NVR - not to each camera separately - and requires your account credentials.
Firmware updates are applied during routine maintenance to patch any vulnerabilities as they are discovered. Ubiquiti runs a bug bounty programme where independent security researchers are paid to find and report issues, so problems are caught and fixed before they can be exploited.
The simplest way to keep a CCTV system secure is to use wired cameras with local storage, keep firmware up to date, and use a strong password. That combination makes it far harder to compromise than any wireless or cloud-based camera system.