Malicious Accounts are accounts that Arctic finds potentially malicious by looking at some of their user information. By looking at the data, Arctic can generate a score, and if the score is above a certain threshold, Arctic will say the account seems malicious.
Yes, you can. Use
a?userinfo <@user> and look for the Malicious Account field.
Yes, you can make Arctic mute, kick or ban people with malicious accounts as soon as they join the server. They'll receive a direct message notifying them about the action (if the DM setting is on), and Arctic will log the event to the logs channel.
Arctic will automatically mute or kick the bot if the setting is enabled. This can help prevent fake or malicious bots that you or your staff may have accidentally added to your server. (Premium)