Google launched the March 2024 spam update on March 5, the same day as the March 2024 core update, and marked it complete on the Search Status Dashboard on March 20, 2024, after 14 days and 21 hours. The announcement post also introduced three new spam policies: expired domain abuse, scaled content abuse and site reputation abuse.
Per Google's definitions, expired domain abuse is repurposing an expired domain to exploit its past reputation with low-value content; scaled content abuse is mass-producing pages to manipulate rankings "no matter whether content is produced through automation, human efforts, or some combination of human and automated processes," an expansion of the old automatically-generated-content policy; and site reputation abuse is publishing third-party content with little first-party oversight to trade on the host site's ranking signals. That last policy did not take effect until May 5, 2024, to give site owners time to prepare. Search Engine Land reported a swarm of pure-spam manual actions right after the policies were introduced.
If your site dropped in the March 5-20 window, review Google's spam policies and remove anything that violates them. The spam update itself was algorithmic, so recovery comes from Google's systems reassessing the cleaned-up site over time; a manual action, by contrast, is reported in Search Console and requires a reconsideration request after cleanup.