DNS servers are the servers to resolve the address that every one in the world type in their web browsers to an ip address to locate the websites. The process is fast and some times hard to notice at the bottom of your web browser status bar.
There was many attacks before on the dns servers to redirect the internet surfers to specific websites for pharming, but the last attack was completely different , same objective but different method,
In Mexico the attackers embedded malicious code inside an email that claimed it had an ecard waiting for you to open it at the website gusanito.com the email also contained an HTML IMG tag that resulted in an HTTP GET request being made to a router, The Get request modified the routerís DNS setting so that the URL for a popular Mexico-based banking site and other domains would be mapped to an attackerís website
An attack like this can be easy to prevented if you set your router a password that way any changes will be impossible to be preformed without entering a correct password, leaving the default password on routers is easy to break because many routers have same default password and that what happened in Mexico they attacked specific router that was popular used in Mexico.