I think RISKS (which he edited) was one of the first places I saw computer security discussed in a meaningful way outside a military context (NSA, Puzzle Palace, Rainbow Books, etc.)

Other mentions of his passing:

- Fwd: [multicians] Peter Neumann has died (lwn.net) 8 points by Tomte | https://news.ycombinator.com/item?id=48172640

- Peter G. Neumann (RISKS) has died (laurenweinstein.org) 3 points by davidgerard | https://news.ycombinator.com/item?id=48169871