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DEF CON 29 - Richard Henderson - Old MacDonald Had a Barcode, E I E I CAR

DEFCONConference · talk · Watch on YouTube

Security & hacking

What it is

A DEF CON 29 talk by Richard Henderson about encoding the EICAR antivirus test string into QR codes and barcodes and scanning them at real systems. Many systems that do not expect such input misbehave or collapse, including a parking garage system.

Why Hacker News recommends it

HN commenters recommend it as an entertaining demonstration of how scanners and antivirus software fail on unexpected input.

  • 4 people recommended it
  • 4 different months
  • 0 strong recommendations
  • first 2021, last 2026

What HN commenters said

  1. “I'd recommended checking it out.”

    DEF CON talk about QR codes.

    grapescheesee, 2022-02 · Recommendation · in “FBI sounds alarm as QR code usage soars”

  2. “I found an interesting Defcon talk about what happens when you turn the EICAR virus signature into a QR code and scan it.”

    Talk on what breaks when scanning an EICAR QR code.

    jrockway, 2023-11 · Recommendation · in “Horrible edge cases to consider when dealing with music (2022)”

  3. “There's a good DEFCON 29 presentation on this topic.”

    Good DEF CON talk; parking system demo at 16m33s.

    Full_Clark, 2025-06 · Recommendation · in “Nitrogen Triiodide (2016)”

  4. “This guy put the EICAR test string into a barcode and started to scan it on various systems, with rather funny effects.”

    EICAR barcode scanned on various systems with funny effects.

    tetha, 2026-04 · Recommendation · in “Claude system prompt bug wastes user money and bricks managed agents”

Excerpts from Hacker News comments, linked to the originals. Summaries and labels were written by a language model from those comments.

Topics: eicar, qr codes, antivirus, def con, input handling

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