Many files with names like this are "bait" designed to get users to download malicious software (like info-stealers) disguised as a text file or a tool to open it.
The text looks like a specific filename for a text document that likely contains Steam account credentials (usernames and passwords) . However, please be aware of the following: Kb3sit4 Steam ACCS.txt
Buying, selling, or sharing Steam accounts is a direct violation of the Steam Subscriber Agreement . Valve frequently bans accounts that change hands this way. Many files with names like this are "bait"
If you are trying to recover your own account or protect yourself, I recommend using the official Steam Support Recovery Tool and enabling for better security. Recovering a Lost or Forgotten Steam Account Kb3sit4 Steam ACCS.txt