Silence on the Wire

Enter Passive Fingerprinting

How does the design of this protocol relate to user privacy? The answer is a bit bizarre: although the design of IP, TCP, UDP, and ICMP packets is generally fairly strict, and the information transmitted in these headers is not particularly verbose, differences in the way various operating systems add information to these packets makes it possible to tell not only the type of operating system in use but even the specific version of an instance of a machine. The differences are particularly evident when dealing with traffic that is not clearly and appropriately discussed in the specification or that is not analyzed during normal quality assurance routines (say, an incoming packets with an illegal combination of flags ...