
1) Computer security 2) Dwarf brother of Fafnir 3) Exploit-based worm
Found on
https://www.crosswordclues.com/clue/regin

Reginn, often Anglicized as Regin, in Norse mythology, was the son of Hreiðmarr and foster father of Sigurd. His brothers are Fafnir and Ótr. When Loki mistakenly kills Ótr, Hreiðmarr demands to be repaid with the amount of gold it takes to fill Ótr`s skin and cover the outside. Loki takes this gold from the dwarf Andvari, who curses it and ....
Found on
http://en.wikipedia.org/wiki/Regin

Blacksmith; son of Rodmar; foster-father of Sigurd.
Found on
http://www.factmonster.com/ipka/A0197623.html
No exact match found.