Update Antivirus signature database behined the firewall

[Mudasar]

Hi,

How can i find that antivirus databses is updating.
What will be the firewall access for live antivirus signature upgrade.

In this file there is a entry /opt/zimbra/conf/freshclam.conf.in
DatabaseMirror database.clamav.net

do i only required http access for this url.

I have find out that clam db is updating after every 2 h by following command
zmprov gacf | grep zimbraVirusDefinitionsUpdateFrequency
zimbraVirusDefinitionsUpdateFrequency: 2h


Thanks