Our masters the CAA say, that each airfields frequency has a protected range, use the frequency outside that range, and you're on your own, so they say.
Unfortunately, they forgot to tell the weather man, who creates high pressure systems, which are conducive to sending VHF signals to ranges unheard of by us mere mortals.
The real pain in the ass is when the likes of Wee Weasily calls at high level, just to say hi, which is just irresponsible.
We share our tower frequency with an airport in Germany, which has the same runway configuration. Frequently, aircraft will call estimating at ----, for the ILS runway --, and we have ATIS information --.
Although we were not expecting the aircraft, in the early days, we commenced overdue action because all those features on that day were identical to our runway in use and ATIS letter.
The only way around it is, if you're not convinced of exactly who you're talking to, ask, and ask again.