Solvedwhen are vac waves?

I was wondering how people know when vac waves are happening, or are they just lying?

Normally, I'm assuming you don't know when VAC Waves are happening

People know vac waves are happening by checking websites that show recently vac'd players. As well with being caught in the wave themselves and reporting detected cheats to forums etc. VAC Waves can happen anytime even as we speak. you can usually expect the more serious waves on Private Providers as their cheats become detected and Thousands or actually hundreds of users get banned on several accounts used to rage and legit cheat.

You can check on the CS:GO reddit page or by browsing the forums and looking at posts that says detected.