Forem: ipusiron

"Shinobi Rokugu" — What a Ninja's Everyday Carry Teaches Us About Physical Security

ipusiron — Wed, 18 Mar 2026 13:34:29 +0000

The Principle: Hide in Plain Sight

In my previous post, I introduced the concept of a "Cyber Ninja." Today, let's look at a concrete example of how ninja thinking applies to physical security.

The key idea is simple: the best tools are the ones nobody notices you're carrying.

Shinobi Rokugu: The Ninja's Six Tools

Traditional ninja carried a standard loadout called Shinobi Rokugu (忍び六具), documented in the ninja manual Shoninki (正忍記, 1681). Six items, each designed for multiple uses:

1. Uchitake (打竹) — Fire Starter

A short bamboo tube with ventilation holes, holding a live ember inside. Used for lighting, cooking, smoke signals, warmth, and — when needed — arson. On night missions, it served as a portable light source.

2. Sanjaku Tenugui (三尺手拭) — The 91 cm Towel

A large towel with surprisingly many uses: face cover, headband, bandage, and more. Most notably, it doubled as a water filter — scoop muddy water through the cloth to make it drinkable. It was sewn into clothing or tucked inside a belt, always within reach.

3. Sekihitsu (石筆) — Soapstone Pencil

A writing tool made of soapstone. Marks could be erased easily and left no permanent trace. Ninja used it to leave coded messages for allies, draw maps of enemy fortifications, and later copy their findings into clean reports after the mission.

4. Kaginawa (鉤縄) — Hooked Rope

A rope with a hook on the end, primarily for scaling walls and fences. But also used to secure small boats, restrain captives, and lock doors shut from the outside to trap enemies inside.

5. Inro (印籠) — Medicine Case

A compact case carrying wound treatment, antidotes, sleeping drugs, insect repellent, poison — and salt. On long mountain missions, salt deficiency was a real threat. Stomach medicine was especially valued, since food poisoning could end a mission instantly.

6. Amigasa (編笠) — Woven Hat

A wide-brimmed hat for sun and rain. But its real value was concealment: it hid the wearer's face from a distance. Small bows and arrows or secret documents could be tucked into the lining. Samurai, ronin, and wandering monks all wore the same style — a ninja wearing one wouldn't raise any suspicion.

The Design Philosophy

Here's what makes this loadout brilliant: every single item was an ordinary traveler's belonging. An Edo-period travel guide called Ryoko Yojinshu (旅行用心集) listed the exact same six items as recommended gear for the road. Nothing would look suspicious at a checkpoint.

This wasn't accidental. Three deliberate design principles:

Blend in — Use common items that don't attract attention.
Multi-purpose — Every tool should serve at least two or three functions.
Always ready — Keep everything on your person so you can depart at any time.

Same Philosophy, 400 Years Later

Modern penetration testers follow the same principles in their everyday carry (EDC):

Ninja Tool	Modern EDC Equivalent	Shared Principle
Sekihitsu (coded messages)	Encrypted USB drive	Record intel without leaving traces
Kaginawa (scaling walls)	Tension wrench + picks	Bypass physical barriers
Amigasa (hiding identity)	Fake badge / hi-vis vest	Social camouflage
Uchitake (multi-use fire)	Multitool / Flipper Zero	One device, many functions
Inro (mission-critical meds)	Backup battery + cables	Keep your gear running
Sanjaku Tenugui (improvised tool)	Rubber ducky / LAN Turtle	Looks innocent, does damage

A tension wrench looks like a hair clip. A USB Rubber Ducky looks like a regular flash drive. A hi-vis vest makes you invisible in a corporate building. 400 years later, "hide in plain sight" is still the strongest play in physical security.

Ninja also built their own tools when nothing suitable existed — the same mindset as a hacker writing a custom exploit or soldering a purpose-built device.

What This Means for Developers

You don't need to pick locks to benefit from this thinking. The ninja's EDC philosophy translates to security design:

Assume the attacker blends in. Your badge system means nothing if someone walks in wearing a contractor vest.
Physical access beats digital defenses. If your server room door can be shimmed open with a credit card, your firewall doesn't matter.
Multi-purpose attack tools exist. A single USB device can be a keyboard, a network sniffer, and a data exfiltration tool.

About Me

I'm IPUSIRON, a security researcher and technical writer from Japan. 40+ published books on hacking, cryptography, and lock sport.

This post is part of my Cyber Ninja series. The full picture is in my book: Cyber Ninja: A Beginner's Guide (Japanese, Shoeisha, Jan 2026).

What's in your security EDC? Or: what's the most creative physical security bypass you've ever seen? Let me know in the comments.

What Is a "Cyber Ninja"? — The World of Full-Stack Hacking

ipusiron — Thu, 12 Mar 2026 18:11:37 +0000

Security Is More Than Code

Security and hacking are like mixed martial arts. They demand information, human, and physical skills all at once. But roughly 80% of security books focus only on the information layer, leaving human and physical security with about 10% each.

This blind spot matters. Physical access can neutralize most digital defenses instantly, and most incidents trace back to human factors: misconfigurations, lost devices, phishing.

I've spent years researching all three domains as one. The result is my book: Cyber Ninja: A Beginner's Guide — The World of Full-Stack Hacking.

So Why "Ninja"?

Ninja infiltrated enemy territory to secretly gather intelligence. Hackers exploit system vulnerabilities to penetrate networks and exfiltrate data. Both erase their traces. The parallel runs deep.

But the connection goes beyond metaphor. In 2021, Ben McCarty of the NSA published Cyberjutsu (No Starch Press) and showed that 400-year-old ninja manuals hold practical insights for modern security training. When that book got translated into Japanese, it hit me hard: an American author had connected Japanese ninja culture with cybersecurity in a way no Japanese expert had done. That shock pushed me to write my own book — not to repeat the same idea, but to propose something new: the concept of a Cyber Ninja.

What Is a Cyber Ninja?

A Cyber Ninja is a new generation of hacker who adapts the spirit and tactics of traditional ninja to modern technology, carrying out covert operations and defensive missions in today's information society.

Think of it as ninja + hacker at the core, borrowing what's useful from spies and the military. The concept is new, but as security challenges keep crossing old boundaries, I believe it will take root.

Key traits:

Gain advantage through intelligence gathering and analysis
Cross the boundaries of information, physical, and human domains
Switch between analog and digital as the situation demands
Overcome difficulties with ingenuity — if the tool doesn't exist, build it

If a Cyber Ninja is the person, then Cyber Ninjutsu is the body of techniques they use — distinct from McCarty's "Cyberjutsu." It covers not only established hacking techniques, but also new approaches that go beyond the current state of the art, primarily from the attacker's perspective.

The Five Conditions of a Cyber Ninja

What does it take to be a Cyber Ninja? I looked at what's expected of jonin (elite ninja), experienced spies, and white-hat hackers, and distilled five conditions:

Technical skill — A trinity approach: information, physical, and human security. Plus solid computer fundamentals.
Ethics — Never abuse offensive techniques. Contribute to society.
Legal knowledge — Understand cybercrime laws and work within them.
Aptitude — Curiosity, passion, creativity, insight, judgment, problem-solving ability, logical thinking, perseverance.
Survival skills — Physical fitness, health management, and preparedness for real-world threats.

#5 surprises people. But threats don't only exist online. Even the most skilled hacker can fall ill or face physical danger. Ninja and spies both prioritized physical conditioning alongside technical mastery — and so should we.

What's Inside the Book

Five chapters, learning from ninja, spies, the military, and hackers:

Prologue — Ninja meets hacker. The definition of a Cyber Ninja.
Knowledge — Ninja clans, spy tradecraft, hacker ideals.
Tools — From ninja lock-bypass tools to hacking devices.
Arts — Ninjutsu to Cyber Ninjutsu.
The Present — Generative AI, dumpster diving, hacking robots, air-gap attacks.

It reads like a catalog — built around excitement and an original perspective, not dry theory.

Bridging Two Worlds

In Japan, the ninja fan base is enormous — almost nobody dislikes ninja. My goal: use that massive audience as a gateway into the hacker world. More people crossing over means more security talent, and that's good for everyone.

What I present is just one school of Cyber Ninja. I call it Mijinko-ryu — the School of the Water Flea.

Why I'm Writing in English

Cyber Ninja: A Beginner's Guide is currently available only in Japanese. But after 25 years of writing about security in Japanese, I feel strongly that the Cyber Ninja concept deserves a global audience. So I'm sharing the ideas here on dev.to, piece by piece. If this resonates with you, follow along.

About Me

I'm IPUSIRON, a security researcher and technical writer from Japan. 25 years in the field, 40+ published books on hacking, cryptography, and lock sport.

Full details: Cyber Ninja: A Beginner's Guide (Japanese, Shoeisha, Jan 2026).

Next: the ninja's six everyday tools — and how they map to a modern pentester's EDC.

What's the most "ninja-like" security technique you've encountered? Drop your story in the comments.