On Sun, Oct 22, 2023 at 5:47 PM Job Snijders via NANOG <nanog@nanog.org> wrote:
On Sun, 22 Oct 2023 at 17:42, Amir Herzberg <amir.lists@gmail.com> wrote:
Bill, thanks! You explained the issue much better than me. Yes, the problem is that, in my example, the operator was allocated 1.2.4/22 but the attacker is announcing 1.2.0/20, which is larger than the allocation, so the operator cannot issue ROA for it (or covering it). Of course, the RIR _could_ do it (but I don't think they do, right?). So this `superprefix hijack' may succeed in spite of all the ROAs that the operator could publish.
I'm not saying this is much of a concern, as I never heard of such attacks in the wild, but I guess it _could_ happen in the future.
How is “success” measured here?
The attacker won’t be drawing traffic towards itself destined for addresses in the /22, because of LPM https://en.wikipedia.org/wiki/Longest_prefix_match
Attackers don’t hijack IP traffic by announcing less-specifics. It don’t work that way.
Even for positive ROAs (not AS 0 ROAs), that depends on how much of a region's routers have full-routes or use partial routes. In Brazil there are still many Mikrotik devices being used by BGP-speaking networks that fumble on full-routes, and the offending announcement might not have a LPM to choose from. That might be yet more prevalent in routers connecting to IXPs, because even default-route networks would see those announcements without a LPM to follow. Rubens