by immibis | 2025-06-21 22:51:46+00:00
The simplest is to just wait until the attacker is bored, and/or daddy's credit card runs out.

If you aren't doing any business, or not much business, through your site, this can be fine. Your hosting provider may either choose to let your server be overwhelmed with as many packets as its pipe can fit, or it may need to protect its network by discarding traffic to your IP address upstream of itself. It's probably a good idea to reach out to your hosting provider and let them know you're getting DDoSed. Even if they can't do anything about it (though there's a chance they can) they'll hopefully appreciate the heads up.

True story: I ran a Pixelflut client for 38C3 from a Netcup server in Nuremberg (this somehow had better performance than running it on my tablet at the physical location) and they somehow thought 38C3 was DDoSing me and "helpfully" blackholed traffic between 38C3 and my server.

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It's important to stop thinking of DDoS as some magic hammer of Thor that you can't do anything about. DDoS packets, like all other packets, have source and destination addresses and flow through routers and links.

When Cloudflare receives a 7-terabit DDoS, they aren't receiving 7 terabits through one link. Cloudflare operates a huge number of locations that pretend to be one coherent network. So they're receiving 100 gigabits in London, 100 gigabits in Frankfurt, 200 gigabits in NYC, etc. Their network architecture pretends like it's delivering all these packets to their destination addresses, but really, each location has its own completely different set of servers that all have the same addresses. (This is called anycast.) Each individual packet sender is only sending packets to the nearest Cloudflare node, where they're getting discarded. Likely, no individual node is overloaded by this, but when you aggregate the statistics from all of them, it adds up to a large amount of traffic. This is by the nature of a DDoS - it's devices all over the world attacking you, which means they're all coming by different routes.

It's similar with hosting providers too, at least the big ones. Suppose you're on Hetzner: https://www.hetzner.com/unternehmen/rechenzentrum/ . They're not getting a terabit against your server through one link - they're getting 100Gbps through DE-CIX Frankfurt, 10Gbps through AMS-IX, 50Gbps through Telia in Nuremburg, 50Gbps through Telia in Helsinki, 50Gbps through Core-Backbone, etc.

If they deploy a routing rule to the router on their end of each of those links, which says to discard packets where the destination address is yours, they can protect their network. Your site will still be down, of course.

If one of their pipes does get overloaded (say their full 10Gbps from Baltnet in Frankfurt), they can reach out to that network (pretty much every serious network on the internet has a network operations center, reachable 24/7 by phone) and Baltnet will track it down further and block the traffic even closer to its source (or at a wider part of their network).

If you're lucky and the DDoS traffic is just coming from a few "directions", users whose packets happen to come via a different direction may still be able to access your site.

Suppose you're on Uncle Tom's Tiny Hosting Company Ltd (not real), they're certainly not the scale of Hetzner, and they only have a 10Gbps pipe between them and their ISP which is easily filled by a single attack. They'll have to contact their ISP to block traffic to your server so that the rest can get through, and their ISP will do the above stuff.

None of this information will keep your site up during a DDoS, I just want to show you there's a depth to this DDoS thing and this Internet thing and it's not just magic.