This is the official developer writeup for the challenge 'Outage - The usual suspect' that was created for the Digital Overdose Autumn 2021 CTF.

The two other writeups published for this event are:

• A door by any other name
• C1 - I think this should be C4

Summary

• Challenge description and statistics
• Context
• Writeup

Challenge description and statistics

The text reads:

Digital Overdose has a website, and you can access some information about it without really needing to visit, a bit like a phone book of sorts.

Find the flag :)

Out of the 63 correct submissions (First blood by pidnull), this challenge was rated 100% by all contestants.

Context

There is a quite a common meme nowadays when it comes to availability outages on the Internet, because it usually comes down to the same exact type of failure, most accurately summed up by:

Writeup

As such, the title was already enough for most people to solve the challenge. If the player was unaware of this though, that is where the description comes in: What data can you get about a website, without visiting it. Bonus points if it is "Like an address book".

This question has a few simple answers:

• WHOIS data
• Page metadata
• DNS records

When considering DNS, one needs to think about what type of records could be used to store information. The obvious response would be TXT records:

Huh, what's that in line 15? It is a flag!

The flag is DO{1T$_4LW4Y$_DN5}