Defensible Systems Substack

Time for Security Architects to Shift Right

New threats and the need for speed

Mar 10 • Gunnar Peterson

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2

February 2026

Dust, dirt, and identity

Security engineering lessons from the paydirt of the ancients

Feb 4 • Gunnar Peterson

3

2

November 2025

AI's Golden Agent Problem

There are good reasons to think the Agentic version of Golden Ticket - Golden Agent will be worse

Nov 20, 2025 • Gunnar Peterson

4

1

Web Authentication is Broken

Attackers logging in means a new approach is a must

Nov 12, 2025 • Gunnar Peterson

5

May 2025

MCP Security - Thinking in Zones

The New Perimeter is Behavioral

May 17, 2025 • Gunnar Peterson

3

Who will solve MCP Security?

Security Concerns with Model Context Protocol (MCP) for AI Agents and Who Will Solve Them

May 8, 2025 • Alexis Lavi

5

2

1

April 2025

Some Thoughts Pat Opet's open letter

“The game is the same, just got more fierce” -Slim Charles

Apr 26, 2025 • Gunnar Peterson

3

OAuth's Role in MCP Security

Limits and Opportunities in the Identity Layer

Apr 19, 2025 • Gunnar Peterson

10

Join new Defensible Systems subscriber chat

A private space for us to converse and connect

Apr 19, 2025 • Gunnar Peterson

1

March 2025

Starting a Security Program from Scratch

What are the essential tools?

Mar 28, 2025 • Alexis Lavi

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3

Why a Security Architect Also Needs to Be a Good Solution Architect

Or at least have a solution mindset

Mar 7, 2025 • Alexis Lavi

1

February 2025

Identity Security Venn

Is OAuth Impersonation a Feature or Threat?

Feb 20, 2025 • Gunnar Peterson