There appears to be 2 fundamental uses for security cameras - DVR type setups for archival recording and "Live" broadcasting for remote observation.
If remote access is not required, a reasonable level of security can be achieved via segregated networking etc as someone mentioned earlier.
If remote access IS required, all bets are off and you have to decide whether the risk of having your camera accessed by others is a priority. You can take steps to minimize rogue access, but you cannot fully prevent it.
We have 2 cameras set up for remote observation of our dogs while we are at work. If anyone hacked into my feed they'd just get bored. And if they want to watch me come out of the bathroom in a towel, thanks for making me feel better about myself lol.