Briefing:

0xDarkArmy has 1 social account and DarkArmy uses the same name everywhere. Hint: The front page of internet

First off, running python3 sherlock 0xDarkArmy gives us hits on reddit, instagram and twitter, among others.

While nothing interesting was found on the twitter or instagram, there was a qr code posted on the reddit page, seen here

Scanning the qr code, we are directed to a .onion site, openable in tor. see here

At a first look it seems like a static template page. However navigating to /robots.txt we get half of the flag: darkctf{S0c1a1_D04k_

Opening up developer tools and going to the 'networks' tab, we can see that in the get request to the page, there is a custom HTTP header Flag: under Date. This contains the second half of the flag: _w3b_051n7}

Flag:

darkctf{S0c1a1_D04k_w3b_051n7}

So firstly, after seeing what they have said about the eNB ID, MCC, and MNC, I decided to look up what they meant, so :

• eNB ID : used to identify an EnodeB uniquely

• MCC : mobile country code

• MNC : mobile network code

You can distinguish which one is which by knowing that the MCC and MNC are both 3 digits so 81097 must be the eNB ID

We can use the MCC and MNC to find out that the cell tower is in the US, and that its provider is AT&T. Now we need to triangulate the cell tower so after a bit of googling I found a website called cellmapper.net, where you can specify the eNB ID, MNC and MCC, so finally you get the latlong coordinates by clicking on the location, which are 32.8464489 and -24.554806.

Flag:

Because we know that the briefing says the format is darkCTF{latitude, longtitude} to 1 decimal place we know that the flag is DarkCTF{38.4, 24.5}