Suppose a future where the security counters measures against the DoS attacks are much more widely implemented than at the present. In this future network, anti-spoofing and the directed broadcast filters are globally deployed. Also, security of PCs and workstations is much greater, making creation of the bot nets difficult. Explain whether the administrators of server systems still have to be concerned about, and take the further countermeasures against DoS attacks, if so, what kinds of attacks may still happen, and what measures can be taken in order to decrease their impact?