The Homeless Bifid Cipher
[ranking: 7]
Status: Sort of solved
In 2013, someone posted a story on Reddit about a homeless man handing them $50 and a note full of jumbled letters that the internet quickly realized was a Bifid Cipher. Redditors who went down the rabbit hole transcribed names into IP addresses, figured out UNIX codes, and tracked down retired professors, while other users, possibly with less time on their hands, called BS on the whole thread.
What's Happening On Mount Chiliad?
[ranking: 17]
Status: Unsolved, but also fictional
Mount Chiliad is an area within Grand Theft Auto V that features alien abductions, a mysterious mural, and a weird red blinking thing. Normally, an in-game mystery wouldn't be a big deal, but so many users have banded together to try to solve this fictional UFO case that it's worth mentioning.
Some Redditors have even discussed building a website specifically for solving the case.
The Old Tape
[ranking: 16]
Status: Dubious, at best
In 2013, audio of an unknown origin showed up online that was allegedly recorded while a user on 4chan's /x/ board was flipping through stations on the AM dial in the mid-'90s. Redditors argued a few different points about the audio, but mostly came to the conclusion that the spooky voice was probably an art project.
Does anyone else get the feeling that "art project" is code for "This is definitely a ghost"?
Cicada 3301
[ranking: 4]
Status: Solved
The Cicada 3301 puzzle appeared in 2012 along with the following message:
Hello. We are looking for highly intelligent individuals. To find them, we have devised a test. There is a message hidden in the image. Find it, and it will lead you on the road to finding us. We look forward to meeting the few who will make it all the way through. Good luck.
Wouldn't you know it, a Swedish cybersecurity researcher just happened to have the steganography software and knowledge of the Mayan language to solve it.

Sad Satan
[ranking: 19]
Status: Solved(ish)
For something with as cool a name as "Sad Satan," the viral mystery was too good to be true. What started as a "deep web horror game" with hidden references to pedophilia rings, quickly turned into something that definitely contained illicit images of children and may have been created by the owner of a YouTube channel to increase views.

The Song
[ranking: 22]
Status: Solved... and groovin'
In 2014, a Redditor heard a song in car commercial and wanted to find out who recorded it. It was a simple enough task that turned into a full-blown mystery when the Redditor realized that other users were searching for the same track.
After a few dead ends, the user was contacted by another Redditor who directed them to Spotify, where the track was streaming. Was it worth it?
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