Hi there.
DSL, if you are trying to open a ".pdf" file you need Adobe's reader, and it IS freeware, and all web brousers are aware of this and will ask to install adobe reader in order for you to see the file, even if you already have an older version of adobe reader (aka Acrebat), so it is hard for me to know if it is an attack or just the brouser doing it's job.
So, could you tell me which site is it that you experienced this event, so that i may see for myself?
Also if it is detected as an attack, it may verry well be one, if you d/l and read ".pdf" files you do need adobe reader, you should get from adobe direct @
www.adobe.com it is freeware, but there is a licence agreement when you install it.
JohnDowe.