An ordinary fox (여우, yeou) — as opposed to the nine-tailed gumiho covered in its own article on this site — is read more neutrally as wit and adaptability, without the gumiho's specific undertone of seduction and danger. It's worth keeping the two separate, since Korean dream interpreters generally do: a plain fox and a gumiho are treated as genuinely different symbols, not degrees of the same one.
Outsmarting a fox in the dream, or watching a fox cleverly solve a problem, is read favorably — bettering a sharp, capable rival, or successfully navigating a situation that calls for wit rather than force.
A fox simply observing you from a distance, without acting, is read as someone clever currently watching your situation — not necessarily with bad intent, closer to a shrewd, cautious presence than an active threat.
A fox that seems to be leading you somewhere, whether helpfully or misleadingly, is read through the dream's overall tone — a calm, confident fox is read as useful guidance, while an unsettling one edges closer to the gumiho's more cautionary territory, worth reading in light of that related article if the feeling was genuinely uneasy.