Nachi worm fought Blaster and patched systems — but still took down networks
neuroecology · x · 2026-09-05
Continuing his agents-as-worms thread, the author recalls the 2003 Nachi (Welchia) worm: it exploited the same Windows RPC vulnerability as Blaster, but instead of wreaking havoc it deleted Blaster, downloaded and installed Microsoft's security patches, and even sealed the hole it used.
Yet it still caused damage:
- Its scanning and patch traffic flooded networks; the US State Department shut down its network for 9 hours to remediate.
- Microsoft said the worm was not always successful at applying patches.
- It self-removed on January 1, 2004 or after 120 days.
The lesson: even a well-intentioned self-replicating agent can do systemic harm — a fitting historical footnote for today's AI agents.
Related event: From Morris to Nachi: Worm History as a Mirror for AI Agents(2 posts)→
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