Zamunda.net is the biggest and the best tracker in Bulgaria. They offer lots of content with many peers and pretty decent speeds. Tracker was founded around 2006, maybe earlier can't give you exact date with the name Torrent.linkos.bg. They've changed it later to what's now.
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If you choose your language to be bulgarian then you'll see the bulgarian forum which is massive in size
Registered users: 700,000
Big part of the users have multiple accounts. They don't care much for that. Tracker is open for registration but is usually full. So take a good care for your account because sometimes it's very difficult to register, even this can take months. As for cheating, there are no problems to cheat them. I tried it personally with very high speeds and they didn't caught me. But after all I'm from Bulgaria and I have a decent connection. I'd recommend a speeds around 200-400kb/s for cheating. Using the latest build of the good programs here will ensure you