Hikvision has had some security issues with their cameras and NVRs in the past. Recently they have released a white paper and webinar about what they are doing to make sure their products are secure.
The main thing to remember is to change the password on your equipment to a strong password. Never keep the default password. Most "hacks" you hear about regarding security cameras is simply because the user never changed the default password and they opened the camera up to the internet.
Security Webinar: Addressing and Preventing Cyber Threats