Stealerium is the name of an infostealer malware. The malicious application is written and compiled using C#.
When it deploys on a victim system, Stealerium starts recording logs and exfiltrating information from the host computer. The logs are then transferred to a Discord server run by the malware's operators. To connect to the Discord server and transmit the log data, Stealerium used a webhook.
Stealerium attempts to scrape and steal a large array of information that can be potentially stored on the victim's PC. This can include data such as passwords stored in the browser, history and bookmarks, and cookies. The malware can also gather information from a number of popular VPN applications.
Game clients and launchers are also scraped by the Stealerium infostealer. The malware can collect information from the Minecraft launcher and Activision's Battle.net.
The malware also has keylogging and cryptojacking capabilities. It can monitor the system clipboard for cryptowallet strings stored in it and replace them with a hardcoded string that matches the malware operator's cryptowallet, effectively redirecting and hijacking crypto transfers.
Malicious applications of this type are often distributed through illegal torrents of paid software and websites that offer "cracks" for subscription-based or paid applications.