IE 6 dosen't close port 139. It's used for file shareing. Check your network settings to make sure you have it off or restricted to certain users. If you do have it restricted for certain users, encourage them to use strong passwords that are not easily guesed. It's a slim to none chance some one is trying to nuke you on port 445. Here's the Dshield stastitics for the amount of attacks on port 445: http://www1.dshield.org/port_report.php?port=445

If you're really woried about it then you may want to look into a firewall. Hardware or software, personally I use software. I'm guessing you're on windowz so I would recommend Agnitum Outpost. You can download it here: http://www.agnitum.com/download/outpostfree.html

Hope this helps.