olemus
üks lingikuulutuse viise avaldaja teavituseks linkimisest
= a message sent to a website when a link has been created to this website from another website

ülevaateid
https://en.wikipedia.org/wiki/Pingback

https://www.w3.org/wiki/Pingback

turvalisus
https://conetix.com.au/blog/analysis-wordpress-pingback-ddos-attack/