every system has it's weaknesses.
linux is not immune from this either, but all the tools to manually secure a network are built in and some have guides on the internet as how to secure them.
do you honestly believe a system used to connect 30,000 people is going to be easy to secure? and those people need to do computer tasks and office tasks and make art and special effects etc.
keep in mind Microsoft claims all it's products are 'secure' if you patch them. all the real windows security content i've paged through is essentially boils down to this... don't connect it to an unsecured line. that is insanely easy to breach with a cell phone. which is why hospitals say not to use a cellular device and have a desktop background that identifies itself as being a medical computer and that it is against the law for unauthorized use.
seriously the security is a desktop wallpaper. and of course the electronic firewall. i remember when you needed winsock.dll to connect a windows machine to an internet connected device, like a unix machine. linux for the desktop is a little better than windows security but intrusion detection and prevention is still needed on any system that pretends to be secure.
the fact that very few people actually know what they are doing only makes the problem worse, and the vast majority of the 'best computing practice' boils down to 'use a firewall to pretend like you don't exist on the internet' however truly free software enables security though many methods including obscurity and through knowing what every command does and how it was developed and what really works.a series of admins who know what they are doing can in fact make a secure network and have secure communication. but the people willing to learn that much complex stuff are rare. it is a task better suited to an artificial intelligence than a human being. as an artificial intelligence can quickly scan almost every thing it takes a human hours to do, in mere seconds. however without the human the machine has no one to imitate, so there need to be people who really understand computer networks to assist the machine in keeping systems humming even on the internet, where for some bizarre reason people willingly connect devices with the hope of having fun or getting paid money, while also putting those devices at risk if they are not properly secured, and any insecure line those devices may open for their general use.