A method for determining the presence of an unauthorized femtocell in a network, said network comprising one or more authorized femtocells providing overlay coverage within a building in an overlay configuration with a macrocell tower, the method being performed by a processor within an apparatus and comprising the steps of: capturing a baseline sample for the network, wherein the baseline sample comprises a plurality of measurements obtained from one or more measuring instruments disseminated inside the building across a plurality of downlink radio frequency RF bands within the network wherein while the baseline sample is captured, it is ensured that transmissions from unauthorized femtocells do not occur; and storing the captured baseline sample as a plurality of RF signatures in a database; monitoring the network to identify an RF signal, wherein identifying an RF signal means determining, based on further measurements obtained from said one or more measuring instruments across one or more of said downlink RF bans, a RF signature of said RF signal, wherein each of said measurements and said further measurements comprises at least RF signal strength measurements, such that each of said stored and determined RF signatures comprises at least a plurality of RF signal strength measurements collectively representing a frequency spectrum; determining from said RF signature if the identified RF signal has a signal strength value exceeding a predetermined threshold, wherein the value of said threshold is such that no macrocell towers transmit signals having a value above said threshold, as measured within said building; determining whether the baseline sample does not include the identified RF signal having a signal strength value exceeding the predetermined threshold by comparing the RF signature of the identified RF signal with the plurality of RF signatures stored in the database to determine a match therebetween; and determining the presence of a said unauthorized femtocell in the network when the baseline sample does not include the identified RF signal exceeding the predetermined threshold. capturing a baseline sample for the network, wherein the baseline sample comprises a plurality of measurements obtained from one or more measuring instruments disseminated inside the building across a plurality of downlink radio frequency RF bands within the network wherein while the baseline sample is captured, it is ensured that transmissions from unauthorized femtocells do not occur; and storing the captured baseline sample as a plurality of RF signatures in a database; monitoring the network to identify an RF signal, wherein identifying an RF signal means determining, based on further measurements obtained from said one or more measuring instruments across one or more of said downlink RF bans, a RF signature of said RF signal, wherein each of said measurements and said further measurements comprises at least RF signal strength measurements, such that each of said stored and determined RF signatures comprises at least a plurality of RF signal strength measurements collectively representing a frequency spectrum; determining from said RF signature if the identified RF signal has a signal strength value exceeding a predetermined threshold, wherein the value of said threshold is such that no macrocell towers transmit signals having a value above said threshold, as measured within said building; determining whether the baseline sample does not include the identified RF signal having a signal strength value exceeding the predetermined threshold by comparing the RF signature of the identified RF signal with the plurality of RF signatures stored in the database to determine a match therebetween; and determining the presence of a said unauthorized femtocell in the network when the baseline sample does not include the identified RF signal exceeding the predetermined threshold.