So I was uh, downloading some linux isos, like usual. It was going slowly, so I opened up the Trackers tab in qBittorrent and saw the following:

Most of the trackers were totally dead. Either the hosts were down or the domains weren’t being used.

That got me thinking. What if I picked up one of these dead domains? How many clients would try to connect?

What are trackers for, anyways?

A tracker is a core component of the BitTorrent protocol. Trackers are the services that point you to other peers for the torrent. Without trackers, there would be no one to share the file with.

Obviously this represents a major source of centralization in the torrent protocol. If your trackers aren’t maintained – or if they get forced offline by certain industry organizations – you’re out of luck.

We have an alternative, called Mainline DHT, which performs a more decentralized lookup of peers based on infohash alone. DHT isn’t perfect, though. It relies on bootstrap nodes and is vulnerable to Sybil attacks. And in the example of my poorly-served torrent, DHT wasn’t surfacing any peers, regardless.

Hosting a tracker

Looking through the list of trackers marked “host not found”, I noticed udp://open.demonii.si:1337/announce was available.

I bought the domain through Dynadot (one of the few .si domain registrars), then spun up a quick anonymous VPS. I mapped the domain to the VPS, then set up opentracker, the most widely used and robust torrent tracker software.

Instructions for Ubuntu 24.04:

sudo apt install gcc-14 g++-14 build-essential zlib1g-dev
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-14 14
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-14 14

Follow the readme to compile, first the dependency libowfat (a GPL reimplementation of some of dan bernstein’s C libraries) and then opentracker itself.

cvs -d :pserver:[email protected]:/cvs -z9 co libowfat
cd libowfat
make
cd ..
git clone git://erdgeist.org/opentracker
cd opentracker
make

Finally, a quick systemd unit file to daemonize this service:

[Unit]
Description=opentracker
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
User=opentracker
Group=opentracker
WorkingDirectory=/var/lib/opentracker
ExecStart=/home/opentracker/opentracker/opentracker -p 1337 -P 1337 \
          -d /var/lib/opentracker -u opentracker
Restart=on-failure
LimitNOFILE=65536

[Install]
WantedBy=multi-user.target

What did I find?

Before even starting opentracker, I saw a flood of traffic against UDP port 1337:

I then started the tracker. After about an hour, it peaked at about 1.7 million distinct torrents across 3.1 million peers!

Response from http://open.demonii.si:1337/stats?mode=everything:

  273419141
  
https://erdgeist.org/gitweb/opentracker/commit/?id=b20b0b89264e9d28ab873b8b1cc9ba73cdb58aeb
  
  10313
  
    1735538
    1735523
  
  
    3155701
  
  
    1342504
  
  
    244224
  
  
    
      21532
      20219
      263
    
    
      58843612
      18321703
      33160261
      3211543
      4116689
    
    
      0
    
  
  
    
       interval="00">12216193
       interval="01">1463740
       interval="02">536527
       interval="03">284756
       interval="04">243276
       interval="05">93237
       interval="06">63618
       interval="07">53934
       interval="08">36851
       interval="09">28990
       interval="10">352150
       interval="11">56610
       interval="12">24557
       interval="13">21628
       interval="14">24932
       interval="15">63250
       interval="16">38174
       interval="17">33730
       interval="18">27827
       interval="19">27166
       interval="20">22463
       interval="21">17820
       interval="22">17248
       interval="23">17276
       interval="24">17825
       interval="25">20144
       interval="26">27987
       interval="27">792338
       interval="28">1579577
       interval="29">1625355
       interval="30">2229105
       interval="31">1670317
       interval="32">1581574
       interval="33">846355
       interval="34">96656
       interval="35">68160
       interval="36">47801
       interval="37">36705
       interval="38">32256
       interval="39">27535
       interval="40">27593
       interval="41">27640
       interval="42">24090
       interval="43">20762
       interval="44">17880
    
    
       code="302 Redirect">0
       code="400 Parse Error">0
       code="400 Invalid Parameter">55
       code="400 Invalid Parameter (compact=0)">0
       code="400 Not Modest">0
       code="402 Payment Required">0
       code="403 Access Denied">0
       code="404 Not found">883
       code="500 Internal Server Error">0
    
    
      0
    
  

Is this legal?

Maybe.

When the recording industry and other litigious organizations go after torrent trackers, they’re mainly chasing down the public-facing parts of the system. The legal decisions against websites like The Pirate Bay hinge on how they highlight popular movies, sell ads, and offer .torrent files. This is all taken as evidence of inducement, meaning the intentional promotion of copyright infringement.

Does hosting tracker infrastructure, unadvertised, count as “inducement”? It’s a harder case to make. I’m aware that many torrents, both freely available and copyrighted, use this tracker. But it would be more difficult to prove intent here.

Regardless, I was spooked. I thought through my chain of events and realized I had already fucked up by paying for the domain with a credit card. I shut down the VPS and deleted the domain quickly after confirming it works.

So… the domain is available now. It’s quite easy to find unclaimed domains like this. If you want to do a public service, open.demonii.si and others are up for registration…