If it's the thorny thing, it's Blackberry (Rubus sp.): I cannot be more specific about it because there are several closely related species plus many many spontaneous hybrids between domestic cultivars and wild species.
What I can tell you is that Blackberry is easily and quickly dispersed by birds, grows very fast and that it will quickly become a major invasive (sensu stricto), especially in degraded habitats such as abandoned gardens, poorly managed woodland etc.
General rule of thumb is to eliminate it, quickly, unless you want to harvest blackberries for consumption: in that case the best solution is to have a small patch where blackberry vines can be easily managed, both to keep them tidy (and productive) and to avoid birds feasting on berries.
Blackberries are usually eliminated with large displacement (>30cc) high quality brushcutters using a specific cutting head like this:
https://www.amazon.it/JOANS-Ma... They are first cut (from top to bottom) and then ground to tiny bits when on the ground. Or if you have a tractor with a cutter/shredder, you'll save yourself a lot of sweat.
