10. A host of unresolved issues remain

Achtung Baustelle How does the HTTP Server redirect queries to a specific website?
(Name-based Virtual Host Support)

Achtung Baustelle How does an FTP Server place a customer in its private directory?
(PAM with virtual users and Chroot jail)

Achtung Baustelle Why does a single Mail Server accept emails for many domains?
(Relaying with qmail)

Achtung Baustelle What is a "virtualized email service"?

Achtung Baustelle How does dynamic DNS work for static/dynamic IP addresses?

Achtung Baustelle Why does a CDN, especially one based on P2P (e.g. CoralCDN [which is unfortunately offline at the moment]) make it difficult to identify a server address?

Achtung Baustelle Why do Public Proxy Services (e.g. CyberGhostVPN) make it difficult to identify a client address?

Achtung Schleudergefahr How do you know that log file entries were created by queries from the TOR (network) and it would be a waste of time to try and find out who the subscriber is? (Click for more details.)

$ curl -s https://check.torproject.org/exit-addresses \
| awk '/ExitAddress/ { print $2; }' \
> /tmp/tor-exit-addresses
$ while read IP ; do
    if grep --fixed-strings "${IP}" /tmp/tor-exit-addresses \
    > /dev/null 2>&1 ; then
      printf "${IP}\n"

If you want tor exit nodes to be filtered out, just insert "--invert-match" after "--fixed-strings".