Unless modded, the abduction can't be canceled, targeted sims will stop whatever they're doing to investigate the weird light. But you can stop it by disallow your targeted sim to go outside! Just lock all the doors which lead to outside! Click the door then choose the lock for everyone, your sim will be safe from abduction. And remember to unlock them or sims can't enter or leave the house.
There is an hidden bar which determines the chance of abduction. I found out the "search for the truth" will strongly enhance the chance. I've read some feedback on the abduction, players had replied that having higher logic skill, using rocket, owning space rock or alien item form space, travel to the alien home...anything related to alien will fill the abduction bar. And it seems that interacting with aliens, including disguised ones, will encourage sims to be abducted as well. That's why doctors and scientists tend to be abducted more often, because they more or less will meet some aliens at work. So if you don't want to be abducted, just don't do such things to trigger it.
