Basically, it's submitting hidden sell orders at a high price, and submitting a lot of visible buy orders in the hopes that other people pile on and bid the price up to your sell order. It's market manipulation, and it wouldn't even work if you DOSed other people's computers. The goal is to fool them into filling your orders at unfavorable prices - a DOS would simply shut them down.
Basically, it's submitting hidden sell orders at a high price, and submitting a lot of visible buy orders in the hopes that other people pile on and bid the price up to your sell order. It's market manipulation, and it wouldn't even work if you DOSed other people's computers. The goal is to fool them into filling your orders at unfavorable prices - a DOS would simply shut them down.