Love GranniE Writeup - DownUnderCTF 2025

OSINT/Love GranniE - a_metre

Hello dear, it’s your Grannie E.

My lovely nurse took me out today and I found where I used to go see movies! Back in my day movies didn’t talk or have sound! How the times have changed. I’ve added in a photo from back when I used to live there, with help from my nurse.

I’m going for a cuppa now, will call later.

Love,

Grannie E.

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Given the image from Grannie E, can you find the name of the movie building, and its current day location? I’ll need a suburb too.

NOTE: Sometimes old records get out of date, you might need to try the street number next door

Flag Format: DUCTF{BuildingName_StreetAddress_Suburb} (case insensitive) - include the street number in the address

Initial Thoughts

We are given a seemingly old photo of a bridge. All we need to do is find where it is, then find a movie theater next to it. Seems simple enough, right? (Spoiler alert: It was, but I overcomplicated it)

Methodology

First, I use Google reverse image search. This yields not 1, but 2 exact matches! Rare for an OSINT challenge.

It seems this bridge is the Epping Bridge.

Now, because the document quite clearly says “Australian Government” and this is a CTF hosted in Australia, one would assume that the answer is somewhere in Australia.

For some reason, I did not come to this very logical conclusion, and instead assumed it was Epping in the UK.

Searching for “Epping UK movie theater old” on Google yields the historic Empire Cinema in Epping, UK.

After finding this, I was convinced that the flag was DUCTF{EmpireCinema_134HighStreet_Epping}. I tried many variations, but none of them seemed to work.

I opened a ticket, and a very helpful (and patient) moderator helped me realize that this CTF is hosted in Australia, and there is an Epping in Australia. I somehow missed that on the document I found earlier about the Epping bridge. In my defense, it was late at night when I was working on the challenge initially.

Google searching “Epping Australia movie theater old” yields the historic Epping Kings Theatre in Epping, Sydney, Australia.

This led me to believe the flag was DUCTF{EppingKingsTheatre_46BeecroftRoad_Epping}. However, that wasn’t working. I knew (or really hoped) this was the theater, so I checked to see if it had any other names.

On that same Cinema Treasures listing, I found out that the theater used to be called Cambria Theatre.

Solution

The flag is DUCTF{CambriaTheatre_46BeecroftRoad_Epping}. This was a fairly easy and fun OSINT challenge, and shoutout to the moderators for putting up with my ridiculousness.