Apparatus (2) for monitoring a set of fuel dispensers (101, 102, . . . 10N) of filing stations (11, 12, . . . 1M), for providing fuel stored in tanks (11) to vehicles, may include interfaces (21) to receive measurements from output probes (301, 302, . . . 30N) measuring fuel flowing through nozzles (111, 112, . . . 10N); measurements from amount probes (31) measuring a stored amount contained within the tank; and receipt data of fuel delivered; a memory (22) to store at least part of said measurements, and a computing means (23). The computing means may be configured for: determining two subsequent fuel deliveries for which stored amounts measured at the start of said deliveries are substantially equals; determining a suspicious situation by comparing said receipt data corresponding to said subsequent fuel deliveries with the sum of measurements provided by said output probes during the time period between these two subsequent deliveries; and triggering an action when a suspicious situation is determined.