A bit more protection for the black hats
Most of the time I don't use 'whois' - except when I want a bit more information to decide if a dodgy looking email that got past Spamassassin is spam or contains dodgy links. However, using the combination of:
* a quick look at the sender and/or embedded domain name with 'whois'
* feeding the domain name through 'host' to get its IP
* feeding the IP back through 'host' to see if it references the original domain.
will often give useful clues about the malignancy quotient of an email and is quick to do.
If GDPR succeeds in making this information inaccessible without providing a replacement malignancy test tool I, for one, shall be extremely pissed off.
Biting the hand that feeds IT
