This paper discusses practical attacks against unencrypted high speed Ethernet links. There is a common misconception that the sheer amounts of data which can be transferred using multiplexed channels (e.g. WDM technology) make successful attacks highly unlikely. We will show that a skilled and motivated attacker can easily identify and extract sensitive information if he observes/collects a large amount of raw data and, more importantly, will be able to do so in a feasible manner as for the time or technical resources needed.