In the case of a local network, the security cameras are not usually passworded, since the network security it self is considered to keep malicious attack at bay, so the hacker would have to do little else to take control of the camera and typically other devices around the house.
A security camera which transmits video feed over the internet could fall victim to password attacks like weak or default password and also attacks that circumvent authentication on the security company's web servers altogether.
The other way for an hacker to find an unsecured video feed is only a Google search away. Their are ways to know if your security camera has been hacked.
It would be very difficult to know if your security camera has been hacked,but it could only happen to an untrained person. A red flag for some malicious activity on a security camera is slow or worse than normal performance. "Many cameras have limited memory, and when attackers leverage the cameras, CPU cycles have to work extra hard, making regular camera operations almost or entirely unusable at times.Then again, poor performance isn't solely indicative of a malicious attack -- it could have a perfectly normal explanation, such as a poor connection or signal.
There are precautions you can take for your camera not be hacked
Putting security cameras on a network of their own is also advisable, this would help to prevent "land and expand" where an hacker could gain access to one device which could be also use to control other devices on the same network.
Also, you can use a virtual private network or VNP to further restrict which devices can access the network the security cameras are on, You can also log all activity on the network and be certain there's nothing unusual happening there.
Following the above precautions could decrease the rate and action of the hacker and can also help to provide security, making it difficult for the hacker to take over.