Please answer a question about the following article about Carnival:

Some Belgian cities hold Carnivals during Lent. One of the best-known is Stavelot, where the Carnival de la Laetare takes place on Laetare Sunday, the fourth Sunday of Lent. The participants include the Blancs-Moussis, who dress in white, carry long red noses and parade through town attacking bystanders with confetti and dried pig bladders. The town of Halle also celebrates on Laetare Sunday. Belgium's oldest parade is the Carnival Parade of Maaseik, also held on Laetare Sunday, which originated in 1865.

What group of participants attack bystanders with confetti and dried pig bladders?
Blancs-Moussis