Some people believe in a full stealth firewall to protect them on the Internet full of dangers. A firewall is a necessity, they came in as “scaled-down” server-firewalls. Some people test their ports even several times a day. Does that help? No, an exclusion must be made for port 139: that service better be closed and disabled/or hidden. Furthermore if you start browsing you open up to ports, and it is to be hoped the process that does it is not a malicious node. So the story is a bit different as that it is normally presented to you.
Read this: http://www.pcinternetpatrol.com/page/view/60/
There is one exception when it is helpful to close or stealth a port. It is port 139 occupied by Netbios. Connection to this port could allow unauthorized access to your files because Net BIOS is not password-protected in its default configuration. Therefore, unless you are on the local area network, it is wise to stealth 139.
Whilst most firewalls will be trying to stealth all ports including port 139, there is another measure you can take.
Most firewalls can block NetBios traffic and most users won’t find a problem in there day to day use with NetBios blocked.
I agree with you that your first responsibility is to not use any services you do not need or only and exclusively when you need them. Read about more misconceptions on stealth firewalling here: http://stealthinfo.lockdowncorp.com/
Well, my ISP blocks critical ports by default (like NetBIOS which shouldn’t be accessable from outer internet, just in my local area net (LAN).
It’s cool.
Been blocking NetBIOS for quite some time without any problems. Passed all test on that site except those that tested a proxy which I do not use. Yeah, I know I should.
Still software firewalls stay vulnerable to “wormholes”, through VPN or in another matter traffic can “climb” over the firewall.
Read aboutthis here: http://www.securityfocus.com/infocus/1831
I use a special network monitor that sees packets transferred on a level and in my zone that I cannot see elsewhere, the firewall acts a bit like a “bouncer” in a club, only acts on things he is instructed to react to, but are all customers there that “cool”?