TN-BRIEF/09 · §02 ABOUT REVISED 16 OCT 2026
§02About

Who writes this.

Notes on product security from an engineer who does the job from the inside.

Written by Joseff Lewis.

Tonos publishes notes on product security: prioritising vulnerabilities, running champion programmes, reviewing designs while they are still drafts.

The notes are written by Joseff Lewis, a product security engineer and penetration tester with more than six years across Engine by Starling, Mastercard, Revolut, WithSecure and Synopsys.

Author background

  • A secret-scanning gate that blocks the merge and tells the engineer how to fix it, so leaks are fixed in the pull request instead of a backlog.
  • A vulnerability prioritisation framework based on SSVC, adopted as an engineering standard. Triage by likelihood of exploitation and business impact.
  • A security champions programme, made by engineers for engineers.
  • Security review of architecture decision records at draft stage, now run by a whole security team.
  • Years of continuous penetration testing of applications, from first build to decommission.

Joseff Lewis · Author

tonos τόνος · /ˈtəʊnɒs/ · Greek · noun

The tension by which a thing holds together. In Stoic physics, the degree of tension that turns matter into structure. Also the accent mark: the small mark that changes what a word means.

Author
Joseff Lewis
Based
Brighton
Elsewhere
LinkedIn · GitHub
Views
The author's own, not those of any employer.

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