On November 24th 2023, between 05:35 and 07:00 UTC, a small percentage of Pantheon sites started reporting downtime per internal monitoring. Upon further investigation it was determined that an attacker was affecting Pantheon's routing infrastructure. This lead to an intermittent drop in other traffic, with 503 responses being served from customer sites. We are actively working to reduce our exposure to this sort of incident in the future by tuning rate limiting as well as improving tooling and processes to address malicious activity.