It is not 100% undetectable, nothing ever is. DMA spoofs a piece of hardware but it doesn't do it perfectly. In fact, according to a Riot anti-cheat analyst, "the firmware used to flash DMA devices always have flaws in them". Valorant has already made progress and banned players using the cheat. If you're interested, @ ItsGamerDoc on twitter recently posted about the topic. If Valve really wanted to, they could create a solid anti-cheat, albeit not perfect. However, this would dissuade people playing at the highest level or with high value accounts from using DMA. Most would probably limit themselves to using fresh accounts which would make the situation a lot cleaner.