Internet service provider CenturyLink experienced an outage due to a misconfiguration in one of its data centers. The technical issue affected firewall and BGP routing, thus spread and impacted other internet service providers. Some of the companies affected by the outage are Amazon, Twitter, Microsoft (Xbox Live), EA, Blizzard, Steam, Discord, Reddit, Hulu, Duo Security, Imperva, NameCheap, OpenDNS and led to a 3.5% drop in the global internet traffic, which makes it one of the biggest internet outages ever. CenturyLink announced that the problem is originated from its data center in Mississauga, Toronto.
Cloudflare published a blog post concerning the incident. Cloudflare stated that a bad Flowspec rule caused the issue, which is an extension to BGP, which allows firewall rules to be easily distributed across a network, or even between networks, using BGP. It allows users to efficiently push rules across an entire network almost instantly. Cloudflare also states that it is only a speculation but also a plausible scenario is that the company issued a Flowspec command to try to block an attack. The outage took nearly seven hours to fix and CenturyLink told all other internet providers to de-peer, and ignore any traffic from their own network.