Some ISPs have been redirecting mistyped URLs to pages with advertisements on them. Usually the pages contain ads for related products, or suggestions for what they think the user may have been searching for. Unfortunately, the ads are sometimes hosted on their own servers nad their servers aren’t always secure.

This can lead to users thinking they have arrived at the site they were hoping to, but the page they are actually on might have been hijacked.  Since they don’t know, they may enter their site credentials and get their user/pass stolen by a malicious script.

read more over at Wired.com