Hey Brendan, thanks for the help!

I definitely think you're onto something with the 1337 stuff - I found another instance that just has 牛 so I'm guessing it's a combination of both the typo scenario that became a meme and the duality of "niu". I found another example later on an IT site when Baidu-ing talking about computer classes designed for hackers and 牛 so I'm guessing it means something along the lines of 1337h4x0rs. I'll see if i can find the same link again...