A method of detecting the intervention of a rogue access point in a communication path between a wireless device and one or more resources in a data network reachable via a genuine access point, said method comprising: an authentication message server in the data network: receiving via said communication path, a request issued by said wireless device for an encrypted authentication message, the request including data indicative of an identifier of said wireless device; generating an encrypted authentication message using the received data indicative of said wireless device presented in said communication path, and sending the encrypted authentication message to the wireless device; the wireless device: providing to a comparator in the data network via a previously authenticated access point to the data network,- data indicative of the identifier of the wireless device; data indicative of an identifier of the access point used in the communication path between the wireless device and the data network; and the encrypted authentication message; the comparator: decrypting the encrypted authentication message, and comparing the two sets of data indicative of the identifier of the wireless device; comparing the data indicative of an identifier of the access point to identifiers of known access points previously stored at the comparator; detecting intervention of a rogue access point in a communication between said wireless device and the wired network if said two sets of data indicative of the identifier of the wireless device do not match, and the identifier of the access point does not match identifiers of known access points; and signalling the result of said comparison to said wireless device via said previously authenticated access point to the data network. an authentication message server in the data network: receiving via said communication path, a request issued by said wireless device for an encrypted authentication message, the request including data indicative of an identifier of said wireless device; generating an encrypted authentication message using the received data indicative of said wireless device presented in said communication path, and sending the encrypted authentication message to the wireless device; receiving via said communication path, a request issued by said wireless device for an encrypted authentication message, the request including data indicative of an identifier of said wireless device; generating an encrypted authentication message using the received data indicative of said wireless device presented in said communication path, and sending the encrypted authentication message to the wireless device; the wireless device: providing to a comparator in the data network via a previously authenticated access point to the data network,- data indicative of the identifier of the wireless device; data indicative of an identifier of the access point used in the communication path between the wireless device and the data network; and the encrypted authentication message; providing to a comparator in the data network via a previously authenticated access point to the data network,- data indicative of the identifier of the wireless device; data indicative of an identifier of the access point used in the communication path between the wireless device and the data network; and the encrypted authentication message; data indicative of the identifier of the wireless device; data indicative of an identifier of the access point used in the communication path between the wireless device and the data network; and the encrypted authentication message; the comparator: decrypting the encrypted authentication message, and comparing the two sets of data indicative of the identifier of the wireless device; comparing the data indicative of an identifier of the access point to identifiers of known access points previously stored at the comparator; detecting intervention of a rogue access point in a communication between said wireless device and the wired network if said two sets of data indicative of the identifier of the wireless device do not match, and the identifier of the access point does not match identifiers of known access points; and signalling the result of said comparison to said wireless device via said previously authenticated access point to the data network. decrypting the encrypted authentication message, and comparing the two sets of data indicative of the identifier of the wireless device; comparing the data indicative of an identifier of the access point to identifiers of known access points previously stored at the comparator; detecting intervention of a rogue access point in a communication between said wireless device and the wired network if said two sets of data indicative of the identifier of the wireless device do not match, and the identifier of the access point does not match identifiers of known access points; and signalling the result of said comparison to said wireless device via said previously authenticated access point to the data network.