A method of monitoring an element in a computer network including monitoring a preselected variable relating to that element; defining a threshold for the monitored preselected variable; establishing a sliding window in time; repeatedly generating a time above threshold value, the time above threshold value being a measure of an amount of time during which the monitored variable exceeded the threshold during the sliding window of time; detecting when the time above threshold value exceeds a condition window value; and in response to detecting when the time above threshold value exceeds the condition window, generating an alarm.