SourceHut 被 DDoS 後的報告

SourceHut 在 DDoS 後發表了報告:「SourceHut network outage post-mortem」。

這次的攻擊在 L3 層,直接塞爆 upstream bandwidth:

At around 06:00 UTC on January 10th, a layer 3 distributed denial-of-service (DDoS) attack began to target SourceHut’s PHL infrastructure.

上游 Cogent 選擇 null route 掉:

In response to the attack, Cogent announced null routes for our downstream AS, causing our PHL network to become unreachable both for SourceHut staff and the general public.

中間有試著問 Cloudflare 以及其他的方案,但依照他們的說法,費用上無法承受:

We initially researched a number of solutions, and spoke to Cloudflare in particular due to their ability to provide a rapid response to ongoing incidents. However, given our complex requirements, Cloudflare quoted us a figure which was not attainable within our financial means as a small company. Other options we researched (though we did not seek additional quotes) had similar economical constraints.

後來的解法是在 OVH 放 proxy server (搭配 OVH 的 DDoS 保護服務),然後導到沒有公開的 subnet:

However, we found that OVH’s anti-DDoS protections were likely suitable: they are effective, and their cost is amortized across all OVH users, and therefore of marginal cost to us. To this end the network solution we deployed involved setting up an OVH box to NAT traffic through OVH’s DDoS-resistant network and direct it to our (secret) production subnet in AMS; this met our needs for end-to-end encryption as well as service over arbitrary TCP protocols.

GitHub 在還沒被 Microsoft 併購前 (2018 年) 也有被打的記錄,2015 年的時候 Google 有放一些資料,當年有寫一篇記錄下來:「Google 對 GitHub 先前遭受 GFW 的 DDoS 攻擊的分析」,不過當年這波是 L7 的。

另外 2016 年的時候 GitHub 也有整理一篇關於 TCP SYN flood 的阻擋方式,這個看起來比較接近這次的攻擊:「GitHub 對抗 TCP SYN Flood 的方式:synsanity」。

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