DownUnderCTF 2021

With my growing passion for Cyber Security, I often like to challenge myself and improve my skills wherever I can. In addition, if any competitions embrace the Aussie cyber society, you best believe I will be doing whatever I can to get involved. Fortunately, the DownUnderCTF exists and was back for a second year. The DownUnderCTF is a cyber security competition that explores various security challenges, spreading across different categories such as Web, Open-Source Intelligence (OSINT), Cryptography and more. My main objective for this coemption was to improve my OSINT skills. The following explores one of the challenges I worked on in the OSINT category, called heart of the nation.

The description of the challenge stated

“We found some files on the website (not really), the caption was “Right at the heart of the nation, no piece of the bush inside the circle remains untouched by us”. We believe this is one of their meeting places, can you help us find the location of the photo to three decimal places? Flag format is DUCTF{lon,lat}”

In addition to the description, there was an attached picture, illustrated below.

I tried to reverse image search the photo to see if this picture was somewhere online. However, I did not find much success. My next approach was to see if the image still had some metadata that could help me identify where the photo was located. To achieve this, I used some Linux command tools such as ExifTool, but again my luck ran out, and there was no data to work with.

With no luck from the image itself, apart from identifying critical components in the photo such as the stone hedge, a sign, streetlights, which implied this photo was taken next to a road, my next step was to review the description. The key component that stood out was “Right at the heart of the nation”. I first thought of Uluru and Airs rock which is almost the centre of Australia. However, the landscape did not match what could be seen in the photo. My team member suggested Canberra as it is the nation’s capital, and this made more sense.

Unfortunately, I became a victim of the rabbit hole scenario with this CTF, just like any CTF challenge. The rabbit hole is where you’re confident with your lead in an investigation for those who don’t know. As you follow the path, it’s like following the metaphorical rabbit down the rabbit hole until you realize your lead hits a dead end. It’s hard to stop this, and it can cost a lot of time…It cost me a lot of time ☹ My friend and I were looking for walking trails where there would be land that was “untouched”. So, we thought about aboriginal bushwalks, which could have land that has been preserved. Canberra had quite a few of these.

However, the one thing that we kept questioning was the streetlights in the photo. So, we decided to look up streetlights in Canberra. After some searching, we found a match of the streetlights near parliament house. With this in mind, we took “inside the circle” a bit more literally and realised it was somewhere inside the state circle.

The final step was trying to find where this photo was taken. So, we went to Google maps and tried to drag the little Google Maps yellow man on the road for a street view. However, we were restricted from that. But there were these little circles on Google maps that our little character would snap too. So, we dragged him there, and we could see a 360 view of this location. Although we couldn’t move, we could see a complete 360 picture. With this in mind, we then searched for all these circles. After a process of elimination, we finally found the correct dot.

We copied the coordinates of the photo and compiled our flag  DUCTF{-35.306,149.120}.