it is very easy to recognize and you simply delete all evidence of the signal, the only way to softlock yourself is to send the signal in for points and save (but in that case, resetting objects and events can still salvage the save, though you'll lose all your actual items and stuff...)
that's very good to know! but do you know if there is a way to recognize the signal before downloading it? (similarly to how you can recognize the 'virus' signal, the one that looks like a floating PC by looking at it before downloading it)