It's done by a group who take a stock from nothing to new highs with false volume and higher bids buying at the ask using wash trades between the group. Then they go short and make sure to have enough shares left between them to drop the bid by half at will. They cover and walk away leaving the rest wondering what happened to the big win they were expecting. Some times they linger for months hoping to get their money back before finally taking a near complete loss. IMO