Windows XP Firewall
For more information, visit http://support.microsoft.com/kb/283673.
Click Start, click Run, type Firewall.cpl, and then click OK.
On the General tab, click Off (not recommended).
Click OK
Windows Vista Firewall
For more information, visit http://windows.microsoft.com/en-US/windows-vista/Turn-Windows-Firewall-on-or-off
Open Windows Firewall by clicking the Start button , clicking Control Panel, clicking Security, and then clicking Windows Firewall.
Click Turn Windows Firewall on or off. If you are prompted for an administrator password or confirmation, type the password or provide confirmation
Click Off (not recommended), and then click OK.
Trend Micro Internet Security 2009
For more information, http://esupport.trendmicro.com/Pages/How-do-I-enable-or-disable-the-Personal-Firewall-of-Trend-Micr-EN-1038273.aspx
Open the Trend Micro Internet Security main console by doing any of the following:
Click Start > Programs or All Programs > Trend Micro Internet Security > Trend Micro Internet Security.
Double-click the Trend Micro Internet Security icon on the lower right corner of your screen.
Click Personal Firewall Controls on the left panel.
Under Personal Firewall, click Settings.
To enable the Personal Firewall, put a checkmark in the Activate the Personal Firewall checkbox. To disable it, remove the checkmark.
Click OK
Norton 360 (by Symantec)
For more information, visit https://www-secure.symantec.com/norton-support/jsp/help-solutions.jsp?docid=20081209093552EN&lg=english&ct=united+states&product=home&version=1&pvid=f-home&entsrc=redirect_pubweb
Open Norton 360
Go to Settings > Firewall > Program Rules
Add "bztransmit" if it is not there in the list and select "Allow" from the access menu.
(bztransmit is found in "C:\Program Files\Backblaze\bztransmit.exe")
Screenshot of Norton 360 Program Rules
Click the Apply button
McAfee
Double-click your taskbar icon to open the Security Center.
If you don't see "Configure" at the left then click "Advanced Menu" at the bottom left.
Click "Internet & Network" at the upper left. To the right you will see that you can disable the firewall.
Warning - you will be constantly reminded that the firewall is disabled. To stop that click "Security Center" on the same upper left side menu, then you'll see "Protection Status" at the right, click "Advanced" in that window and you'll see various warnings can be turned off.
ZoneAlarm
I think you just need to configure Zone Alarm to allow the Backblaze software to access the internet. Specifically, you need to allow the executable "bztransmit.exe" to access services on the internet. Here is the relevant Zone Alarm FAQ on how to configure the firewall. By configuring ZoneAlarm this way you can have a firewall and use the Backblaze service.
Instructions can be found here: http://server.iad.liveperson.net/hc/s-28464961/cmd/kbresource/kb-2343038182499907835/view_question!PAGETYPE?sc=21&sf=101133&documentid=347214&action=view
The complete path to bztransmit.exe is "C:\Program Files\Zipcloud\bztransmit.exe"