Lesson pack 14 · Foundation · 90 minutes
Reconnaissance and OSINT
Treat open-source intelligence as a pivot loop rather than a search, and know what metadata survives which route.
Print this page for a paper plan - the navigation and links drop out.Student-facing version
Before the session
- Nothing to install. Students need a browser and https://ctfpal.com. Confirm the room can reach it once; after that it works offline.
- Read the lesson yourself first - about 9 minutes.
- Have one worked example ready to paste. The classroom link builder on the instructor page turns it into a URL that opens preloaded.
Objectives
Written as things a student can do afterwards, so they can be assessed rather than asserted.
- Run the pivot loop: enumerate, expand, cross-reference, record
- Predict which metadata survives a given publication route, and check the right thing first
- Narrow an image's location from visible constraints without recognising the place
- Enumerate an organisation's subdomains from certificate transparency rather than by probing
- State where open-source ends and unauthorised access begins
Running order (90 min)
| Time | What happens |
|---|---|
| 0:00-0:09 | Frame the problemWhat the category looks like when you meet it cold, and why the naive approach fails. |
| 0:09-0:27 | Teach the methodThe technique itself, on the board or from the lesson. No tools open yet. |
| 0:27-0:50 | Demonstrate liveSame technique, in the workspace, on your worked example. Narrate every choice. |
| 0:50-1:21 | Practice setStudents work the challenges. Circulate rather than present. |
| 1:21-1:30 | Checkpoint and wrapCollect the artefact, name what comes next. |
Tools used
- EXIF metadata viewer - Read EXIF, GPS coordinates, camera details, timestamps, and embedded comments from images - the metadata that answers OSINT challenges.https://ctfpal.com/?tool=exif-viewer
- GPS coordinate converter (DMS, decimal, UTM) - Convert between degrees-minutes-seconds, decimal degrees, and other coordinate notations - for EXIF locations and OSINT challenges.https://ctfpal.com/?tool=coordinate-converter
- Timestamp converter (Unix, ISO, FILETIME, HFS+) - Convert between Unix seconds and milliseconds, ISO 8601, local time, and the non-standard epochs used by Windows, macOS, and Flask.https://ctfpal.com/?tool=timestamp-converter
- Strings extractor for binaries and blobs - Pull printable ASCII and UTF-16 strings out of any file, filtered by length, with flag-pattern highlighting.https://ctfpal.com/?tool=strings-extractor
Reading
- OSINT as a method, not a lucky search - 5 min. Open-source intelligence challenges reward discipline over cleverness. The pivot loop, what metadata actually survives, how to geolocate from an image without recognising the place - and where the line is.
- Working a leaked dataset: OSINT on a pile of data - 4 min. Some OSINT challenges hand you a dump - a CSV, a SQL export, a folder of documents - and a question buried in it. The command-line workflow for turning gigabytes of leaked data into the one record that answers the challenge.
Practice set
Real picoCTF challenges tagged with this module’s techniques, easiest first. Assign the first three in class and the rest as homework.
- Bookmarklet - picoCTF 2024, easy
- CanYouSee - picoCTF 2024, easy
- dont-use-client-side - picoCTF 2019, easy
- Includes - picoCTF 2022, easy
- Information - picoCTF 2021, easy
- Insp3ct0r - picoCTF 2019, easy
- Inspect HTML - picoCTF 2022, easy
- Local Authority - picoCTF 2022, easy
- Quizploit - picoCTF 2026, easy
- Scavenger Hunt - picoCTF 2021, easy
- StegoRSA - picoCTF 2026, easy
- Unminify - picoCTF 2024, easy
Checkpoint (gradeable)
Given one photograph with no GPS tag, narrow its location to a city and state which visible constraint eliminated each region you ruled out.
Deliberately a produced artefact rather than a quiz question: it is either there or it is not, which makes it fast to mark and hard to bluff. Every tool in ctfpal is deterministic, so two students who did the work correctly hand in the same value.
Where the room gets stuck
The ethics half is not an aside and should be taught first, not last. OSINT technique transfers directly to real people who did not consent to being investigated, and a class that learns the pivot loop without the line learns half a skill.
If you finish early
- Hand out a challenge from the cross-CTF index in this category - each one has published solutions to compare afterwards.
- Run the same input through Identify and let the class argue with the ranking. Disagreeing with a confidence score is where the technique actually lands.
- Ask a student to break their own example - construct an input that defeats the tool, and explain why.
Take this into a room
Markdown files, built here in your browser. They print, they open in anything, and they carry the challenge text - so the session works with no network in the room.