However, the legislature is not constitutionally limited at the outset to creating, in respect of each type of function, criteria for interferences that reflect the usual model in security law of protecting against specific, directly imminent or present threats. Rather, it can set wider limits for particular fields, in order to aim at already preventing criminal offences, by lowering the requirements of foreseeability of the causal chain. However, the legal basis for the interference must then also require a sufficiently specified threat, in the sense that there be at least factual indications of the emergence of a specific threat to the legally protected interests. General experience alone is not sufficient for justifying an interference. Rather, certain facts must be determined that, in the individual case, substantiate the prognosis that an event leading to an imputable violation of the legally protected interests relevant here will occur (cf. BVerfGE 110, 33 <56 and 57, 61>; 113, 348 <377 and 378>). A sufficiently specific threat in this sense may already exist even where the causal chain leading to the damage is not yet foreseeable with sufficient probability, as long as certain facts already indicate that a threat to an exceptionally significant legal interest may occur. In such a case, the facts must allow the inference of, firstly, an occurrence that can be specified at least with regard to its type and which is temporally foreseeable, and, secondly, of the involvement of persons whose identity has at least been determined to the extent that the surveillance measure can target them specifically and is largely limited to them (BVerfGE 120, 274 <328 and 329>; 125, 260 <330 and 331>). With regard to terrorist offences, which are often committed at unforeseeable locations, planned far in advance by individuals who have no criminal record, and carried out in very different ways, surveillance measures may also be authorised if, despite the lack of a temporally foreseeable occurrence of a specific type, the individual behaviour of a person substantiates the specific probability that the person will commit such offences in the near future. For instance, this is conceivable in the case of a person entering the Federal Republic of Germany after having been abroad at a training camp for terrorists.