Could you please help me how i can update the list with these users ?
If you have the stuff installed that was stated before you should not have a problem, but if you just need to not allow one person to post and you are sure they are not a regular member then you can use some of the vBulletin built in features to block certain IP addresses & email accounts. Go to Settings>Options>User Banning Options and enter the IP address in the Banned IP Addresses box, then enter the full email in the Banned Email Addresses Then click "Save" at the bottom. Be sure in this case to enter the full email address. If you enter just yahoo.com then you will ban everyone with a yahoo address and you may have members who have a yahoo account already.