system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is an open-source OS considered more secure than a closed source?
gpt
For open source systems, the computer code that makes up that system is public, and anyone can read through it. So if someone has left some sort of backdoor or security flaw, it can be caught and fixed. 

Closed source systems have code that's only available to the people who make the software. It could have a dozen backdoors or security holes, and you'll never know unless it gets exploited and someone talks about it.
 
The idea is that if you can see how the system is put together, you can build a more secure system than one that works with code you cant see.