The Winders were the police force of Starship UK, who were actually cyborgs of half-human and half-Smiler. Their heads would rotate around to reveal the malevolent version of the Smiler face (though with a lighter skin tone, whiter teeth, flat nose and brighter eyes). The majority of the time they would wear dark hoods and act as normal Humans, keeping watch on the population. They were under oath to protect the system of Starship UK.
When the Doctor and Amy came to Starship UK, the Winders reported the Doctor's presence after he began investigating the engines. Later, when they learned of the truth, the Winders brought them to Hawthorne to learn the whole story. (DW: The Beast Below)