Hi iflog ,
To solve your issue of filtering undisclosed recipients just follow these steps:

• Goto Tools->Rules and Alerts
• Click "New Rule"
• Select "Move message from someone to a folder"
• In the from filed give the sender field value is "undisclosed recipients" and give the folder you want to move.
• Click finish to save it or you can set more conditions.

If this solvs the issue well and good but if it doesn't then

• Goto Action
• Junk email->Junk email options.
• Add the sender at the blocked senders

Feel free to reply for further issues
~Dex