"... And there came into this world a great darkness. A being of pure hatred with the name of One-by-One-by-One-by-One, or, in later ages, simply The Adversary. 1x1x1x1 is an entity from the fourth dimension who loathes Robloxia for it's 3D-ness and has vowed to destroy it. 1x1x1x1 was imprisoned by Two-by-Two at the dawn of time, yet there are those who seek to free him..."
1x1x1x1 is a Roblox test account and an officially recognized urban legend made by Shedletsky. He is an otherworldly entity and alleged exploiter, with his original account's creation date being 10/24/2007.
While many assume that 1x1x1x1 was a real hacker, the rumor was thankfully debunked by former Roblox admin MrDoomBringer in a forum post. Said post has been pasted below.
"I posted this in a thread that subsequently died. I'm posting it here so you can refer back to it later. Keep the link to this forum. Distribute it. Tell people the truth.
Let's talk about where the name comes from. Long ago, Telamon posted a number of stories about ROBLOX's backstory to the News. One of these included mentions of 2x2, the first brick. Copied over and over, every other brick were it's descendents.
Then, in a footnote, he mentions the evil 1x1x1x1. So that's where the name comes from. Blame John.
Let's talk about why people say he's a hacker. A guy who's name is long forgotten (not Zuka) found an exploit (not CheatEngine) to insert control scripts into online places. He sent me a message, telling me he had something to demonstrate. I joined him in Crossroads, and it started raining heads saying things along the lines of "He's coming back!" and "1x1x1x1 is coming for you!" and the likes. People in the server freaked out, I found it hilarious, he gave me instructions on how it works and I reported it to the devs. End of story.
Other people, like Dignity, would find other way to insert scripts, and people would assume that they have something to do with "the hacker group" 1x1x1x1.
Truth is, it was one guy playing off of a Roblox Lore thing.."