Foros del Web - Ayuda con spam en un foro vbulletin

Buenos dias, tengo esta situacion de spam en mi foro y ya no se como solucionarla.
Es un foro vbulletin.
Se me registran usuarios, pero al parecer esos usuarios son los mismo.
El primero fue weiwei:

Cita:

The local washerwoman replied wow gold that it was perhaps a very wow goldgood plan of Miss or Mrs. Fawley's (as they called her indifferently) to have wow power leveling him with her--"to kip 'ee company in your loneliness, fetch wow power leveling water, shet the winder-shet-ters o' nights, and help in the wow power leveling bit o' baking."

El Segundo fue Pereftiyo:

Cita:

Tom had this problem of getting up late in the morning and was always late for work. His boss was mad at him and threatened to fire him if he didn't do something about it. So Tom went to his doctor, the doctor gave him a pill and told him to take it before he went to bed. Tom slept well, and in fact, beat the alarm in the morning. He had a leisurely breakfast and drove cheerfully to work. "Boss", he said, "The pill actually worked!" "That's all fine" said the boss, "But where were you yesterday?" ----------------------------------Do you look for free wow gold? Welcome to our WoW gold website:1.WoW gold,2.WoW gold,

Y el tercero es Springbirdla:

Cita:

　Teacher:“ I have two questions, it isn't necessary to answer the second question if you know the result of the first question.How much hair do you have?” 　　Student： “ A hundred and twenty millions.” 　　Teacher:“ How do you know it?” 　　Student:“ It is not necessary to answer the second question..World Of Warcraft gold is WoW gold.

con su siguiente firma:

Cita:

World Of Warcraft gold

Todos estos se registraron en Junio.
Hay alguna solucion a este problema de spam?