What Is DNS Hijacking?

Keeping your internet property safe from hackers is hard enough on its own. But as WikiLeaks was reminded this week, one hacker technique can take over your entire website without even touching it directly. Instead, it takes advantage of the plumbing of the internet to siphon away your website’s visitors, and even other data like incoming emails, before they ever reach your network.

On Thursday morning, visitors to WikiLeaks.org saw not the site’s usual collection of leaked secrets, but a taunting message from a mischievous group of hackers known as OurMine. WikiLeaks founder Julian Assange explained on Twitter that the website was hacked via its DNS, or Domain Name System, apparently using a perennial technique known as DNS hijacking. As WikiLeaks took care to note, that meant that its servers weren’t penetrated in the attack. Instead, OurMine had exploited a more fundamental layer of the internet itself, to reroute WikiLeaks visitors to a destination of the hackers’ choosing.

DNS hijacking takes advantage of how the Domain Name System functions as the internet’s phone book—or more accurately, a series of phone books that a browser checks, with each book telling a browser which book to look in next, until the final one reveals the location of the server that hosts the website that the user wants to visit. When you type a domain name like “google.com” into your browser, DNS servers hosted by third parties, like the site’s domain registrar, translate it into the IP address for a server that hosts that website.

“Basically, DNS is your name to the universe. It’s how people find you,” says Raymond Pompon, a security researcher with F5 networks who has written extensively about DNS and how hackers can maliciously exploited it. “If someone goes upstream and inserts false entries that pull people away from you, all the traffic to your website, your email, your services are going to get pointed to a false destination.”

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