By 'backdoors' are you referring to the TeamViewer client they installed on a student computer in the back of a science classroom? If so, suddenly my grandma is now a leet hacker.
That is backdoor, just not particularly leet or advanced. Low skill hacking and backdoor are still hacking and backdoor. Article makes them sound like cybersecurity geniuses, not comment here. Article is all odd.
Imo, the actual tech achievement there (for that age) is building mining computer and learning javascript basics from video. Which is more then other kids can do and shows some self motivation.
Also note the article is pretty explicit that this compromised computer gave them access to the entire network. And "servers" is in plural when it talks about crytpo-mining. Likely this is how they controlled the mining operation.
Imo, the actual tech achievement there (for that age) is building mining computer and learning javascript basics from video. Which is more then other kids can do and shows some self motivation.