I totally don't know what user meant by Cyber Security.
Computer security, cybersecurity or information technology security (IT security) is the protection of computer systems and networks from information disclosure, theft of or damage to their hardware, software, or electronic data, as well as from the disruption or misdirection of the services they provide.
The field is becoming increasingly significant due to the increased reliance on computer systems, the Internet and wireless network standards such as Bluetooth and Wi-Fi, and due to the growth of "smart" devices, including smartphones, televisions, and the various devices that constitute the "Internet of things". Owing to its complexity, both in terms of politics and technology, cybersecurity is also one of the major challenges in the contemporary world. ~Wikipedia
We use Windows, Linux and Mac as our OS system. And, we care of security in our computers not about Android or, IOS. But, I care of Android also.
Cyber security: why does SE not even have this?
Why you are asking question about SE in CD? SE have Cyber Security site also.
We currently have two site for OS systems.
Both had launched at the same time. But, Linux is very inactive site now. PU is active. As you have seen that Linux is very inactive. If there's a Cyber Security site launch than can you say that Cyber Security will be active.
Most of Windows user doesn't care of their security cause, Microsoft company gets most of their information. But, if you have any question related to security than, you can ask in PU as it is on-topic their.
You can ask about Mac system in PU also. Cause, PU is for all available OS system.
Linux is very useful OS for hacking. I had recently seen a hacking related question in Security SE. But, if you ask the same question in Unix SE. Than, it will get lot of downvotes and, it will closed as off-topic (most of time they delete this type of question) maybe. I also point hacking related question as off-topic in Linux CD also. If you want to know more about hacking related question in CD than, you can read the answer. If you have any question about security of your system than, you can ask in Linux