 Welcome back everyone. I want to showcase more of the local CTF or capsule flag competition that I put together as practice as like a local exercise for my school and its cyber team. So this challenge I want to show off is the brisk stroll or brisk stroll. And the prompt is have you seen this image before? There is no hint for this one but the file name is a walkwiththenumber.png. So you would go ahead and download this and I'll zoom out here. You'll see that it is a picture and the ploy or the hope is that they go ahead and save this picture. And the hint that have you seen this before is hey if you haven't already if you haven't seen it you can do a Google reverse image search to go ahead and find where it comes from. So obviously you I guess if you wanted to not knowing you would want to do a little secondography on the thing you can you can run a exit tool on a walk with the numbers. You can run strings on it but it is it is just a regular image file. I didn't I didn't try to pull any tricks with that. However what I did do is I added more to it. So if we did that Google image search total fail we could upload that walk with the numbers that we just uploaded and then it will keep looking for us and it will note that oh it looks like atmosphere okay there's a there's a red herring there but pages that include this image oh it says bin walk for Mac and Linux oh bin walk comments oh bin walk for more analysis tool very clearly I would hope bin walk is what they would be pointed to if they had not seen this or have known of this tool before. So at that point you would end up installing or working with bin walk and I would recommend running bin walk on that file and hey it notices there's the image of course the Zlib compressed data is a fault that bin walk tends to do and it also sees a program in there which is interesting. So we can run bin walk dash e to extract stuff out of it and we would run it on the walk with the numbers and now we see that extracted folder so we can CD into that and it sees this elf file so that's got to be executable so we could run to run that thing and there it is we get our flag cool. USUGA bin walk is a good tool to know so we'll submit that and get our points and I'll show off how I actually put that together. So it's real simple what I ended up doing for one thing was writing out the source code for this program which is again insanely simple it literally just prints out the flag and then I think I put together a create.sh where I would compile the file and they get a 32-bit compile that source code and then I include the image the original image which is just that simple picture and then I'd include that who put this here executable that I just compiled and I just created and then I put it in that I walk with the numbers that I put it in that image that I would upload and use for the CTF challenge so that's really all it is that that executable who put this here was that source code that I would print out the flag and the way that you can include that inside of the image is by actually catting it one after the other because cat will look will output these files in sequence and typically an image viewer once it sees the end of an image it just goes oh that's that's really all that the image is it just displays the image no problem at all but you can use bin walk to see our is there anything more inside this file in which case we had a complete program stuck inside the image so that's why I wanted to introduce bin walk as a tool if they hadn't seen it before if they if they if they have not heard of it so that's how you end up solving and creating that one that's a brisk stroll and we'll move on to some more of these challenges in a future video so thanks for watching guys