I got a bengal boy kitten in June and he is about 6 months old. I have three other cats and ever since he was introduced he jumps on them, bites their necks, and swats at them. The kitten doesn't go outside unless he's in his harness but the others go out whenever they want. As soon as they come in for food and water he immediately attacks. They can barely get some food, and they go right back outside. He's very sweet and sleeps a lot, he doesn't have little energy boosts and goes crazy running all through the house. But his attacks have become a big problem and I don't know what to do.

You shouldn't think of it as malicious. It's what bengals do. It's actually what many cats do, only bengals do more of it.
They are high energy and need a lot of play and physical stimulation. If he was with one of his siblings, they would be engaging in that stuff constantly, and mutually, going back and forth. Cats that age are still learning to be cats, so practicing all the various "moves" that cats have. The chasing, pouncing, "killing", ambushing, defending, fleeing, intimidating etc. He's perfecting what bengals need to become adult bengals, and building up strong muscules and all that.
He has a strong need to do that stuff, and you can't simply suppress that need from him by scolding him etc.

Honestly, this is something that prospective bengal owners who already have other non-bengal cats should carefully consider, because yea, it can be hard on the other cats. I think the best that you can do is to give the other cats options to be away from him. Perhaps give them a separate room where they can eat in peace, and give them places where they can climb up and easily "defend" to be away from him when they just want to chill. But because he doesn't have another suitable playmate, the humans of the house have to fill that role. Consider getting him a cat wheel, get some "dabird" like toys and have some long, hard play sessions every day. You guys created that situation, so you need to make it right for all the cats, including him.

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The little monsters 3

I have a cat that goes in and out and loves to do an "attack" on my bengal. It is not vicious. More like playing, but my bengal doesn't like it at all. You'll have to close your bengal off while feeding the other cats. Just like many human siblings don't get along ... same with pets. Multi-cat households can be a challenge. Like Brian said, you need to really catify your home.