DiscordStealer is a virus that is spread through Discord. It is a Trojan that steals your Discord Session/Token and sends it to the hacker. With your Discord Session/Token, the hacker can log into your Discord account and do whatever they want with it.
They will normally target people with a lot of Discord Server Owners and move the ownership to another account and keep it for ransom.
They will also target people with a lot of Discord Nitro Boosts and move the boosts to another server.
The virus will capture all of your browser cookies and send it to the hacker. This means that they can log into your Facebook, Twitter, Instagram, Snapchat, TikTok, Reddit, etc. so once you recover your accounts make sure to change all of your passwords across all sites and services.