You know those fake "download" buttons you see when you're searching for
old Super NES ROMs completely legitimate open-source software? The kind that advertising networks sometimes spit out even on otherwise above-board sites? Yeah, they're awful, and they often link directly to copycat or malicious files. Google hates them as much as you do, and is taking steps to make them less effective. Starting today, Chrome browsers on all platforms will warn visitors to sites with potentially misleading or fake "download" ads.
The new system is an extension of Safe Browsing, that big red web stop sign that sometimes warns you of possible malware, phishing, or legitimate sites that have been compromised. Safe Browsing is used by approximately a billion web users, at least according to Google, so implementing this warning system could have some very wide-reaching effects. We could be so bold as to hope that the jerks who make these fake download ads might try something else, like jumping off the nearest cliff.
The new changes will also apply to those fake "error" or "virus found!" ads and all manner of deceptive social engineering. The addition to the Safe Browsing warnings won't actually block said ads, so you'll still have to be wary on those few occasions when you visit download sites that are less than scrupulous... which you should be doing anyway.
- Google Webmaster blog