the VAC modules where always present in the linux version of cs go. it was just at the time valve didn't give a stuff about aimtux (the cheat you're talking about) and therefore it took over 6 months for them to add its signature. around late may they added the signature and boom what do ya know a week later everyone who used it got banned. for a while aimtux was quite an obscure cheat, but some youtubers boosted it's popularity by saying it was the best free cheat going, which got valve's attention.
it's still pretty easy to make an undetected cheat on linux. infact, the death of aimtux provides a great copy and paste source to making your own private one. many private undetected forks of aimtux exist.
the rise and fall of aimtux is just one saga of the rampant cheating going on in cs go. i personally think it took valve way too long to get their stuff together as the cheat had a repository on github, and was quite well known in the minority linux cs go community.
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