Hello uroni,
we just noticed that the silent installation of the urbackup client 1.3.1 creates every installation a new firewall rule and did not check if its already there. So every silent installation means a identical firewall rule pops up 
We noticed that because at the moment we have the installer in our login script without checks if urbackup is already installed.
We assumed the installer do the checking if the version is already installed and if the same version is already there does nothing at all.
That would be the best behaivor :), but in the moment the installer runs like theres a clean system.
Could you check that or tell us if its fixable in the NSIS installer?
Any other suggestions?
Otherwise we have to build our own 32bit msi file with a msi wrapper to minimize the firewall impact every time the installer is running (same version or client update situation)
Second possibility for us would be to delete all firewall rules in the script before we start the urbackup installer. Afterwards we add a versioncheck so the installer runs only if there is a new client version.
We’re looking forward what do you think and after that we will see what will be the solution 
with best regards …
swaurbackup