Sorry that the posting may be irrelevant but when I visit sites I do not trust I always use my Mozilla Firefox browser (
www.mozilla.org) - With it you control everything.
All these drive-by installations are because of weaknesses in Internet Exploder. If an IFRAME tag can bypass the general security settings and trick Explorer into believing that the script that is downloaded from god-knows-where has local permissions (as if it is running from your home machine), then we are talking some serious breach...
And what we see is a lot of people exploiting it, maybe for not so noble purposes. Sad but true...