They hunt in packs, often fuelled by alcohol, cocaine and other drugs. Though some are old enough to be fathers and even grandfathers, they're hooked on violence and confrontation, and the well out-of-date idea that by fighting with opposition fans, they're showing support for their club.
Though their numbers have decreased as technology has progressed and the football culture changed, these people are still around. And as we saw at the Euro 2020 Final in London, sometimes you don't need to be actively looking for violence at football to find it.
Where last week was celebrating the passion of football fans, this week we're taking a look at the dark side of fandom: football hooligans.