The British fighters will clash in a middleweight showdown on January 21 in Manchester and Eubank Jr revealed that he has received some furious direct messages from his rival.
He told Sky Sports News: "I've said a lot to him in the build up to this fight. I'm in his head. He even slid into my DMs a few days ago, messaging me on Instagram.
"So I know I've rattled him. I just look forward to finishing off the job on the 21st."
Eubank Jr added: "I actually can't repeat a lot of the language that he used in those DMs. But he is not a happy bunny, let's just put it that way.
"I think that his frustration and his anger is going to play into how the fight is going to unfold. And it's not going to play to his advantage, I know that."
The fighter is confident that he has the ability to overwhelm Smith and has vowed to demonstrate his dominance in the ring.
He said: "I think that there are levels to the sport, there are levels to the game, I think my highest level is going to be too much for him.
"I respect him. He's done a lot in the sport of boxing over many years, as have I. But I feel like at this moment in time we're two separate animals and it's going to be too much for him on the night when that bell goes.
"This is going to be the toughest fight he's ever been in."