A monitoring arrangement (1) for use with a computer network. The arrangement (1) comprises a filtering module (7) which is operable to filter content delivered to a device connected to the network and to generate filtering data indicative of content filtered by the filtering module (7). The arrangement (1) further comprises a connectivity detection module (6) which is operable to detect the connectivity of a device connected to the network and to generate connectivity data indicative of the connectivity of the device. The arrangement (1) is operable to detect when a new device is connected to the computer network and to examine the new device to determine whether the new device is a trusted device. If the new device is not a trusted device then the monitoring arrangement (1) alerts a user to the attempted access by the untrusted device. The monitoring arrangement (1) is also operable to improve the performance of the computer network.