Large LUA download issue

Hi,

We have multiple sites (about 30+ sites worldwide) and servers in each site require to deploy one-week old virus definition according company policy. Thus in this case, we need to deploy LUA in each site. However, we found that everyday each LUA download 7GB! virus definition, it uses up all our local office bandwidth. We have limited bandwidth to internet and all location is separated, thus using a centralize web proxy is not an option here.

We want to know why the Symantec definition files are so huge? 

Do we have any other option in architecture to reduce the download virus definition size? 

Thanks,

Yuen