Hi Luna,

If you mean mechanically tampered with or has had the mileage altered then it can be easy enough to spot. Inspect the car carefully, noting signs of wear and tear, and if the car looks and feels older than the mileage suggests, then it's probably been 'clocked.'

It's also worth getting a history and background check done with Cartell.ie, which should flag up any inconsistencies in its past. 

Finally, the best way to protect yourself is to buy from a reputable seller.