There are a total of 26 Security Camera around Hong Kong. These are more hidden around, they require you to enter a unique number code.
NOTE: At a point on the game you will receive a call from Raymond to meet at a secret location. Raymond will give you a task to do, which is to get a bug from a girl named Not Ping, then you'll plant the bug in Winston's mothers restaurant. After the mission you will be able to contact Not Ping and take her out on a date. You will need to impress her by hacking a Security Camera. Once completed she will award you by displaying all Security Cameras through Hong Kong on your map. To view them on your map, press and it will show all collectibles. Collectibles in white have already been collected, collectibles in grey have not been collected.
Here is a great video location guide of all Security Camera by Prendi.