The cyberattack that resulted in nytimes.com and some other high-profile websites being inaccessible to a large number of users Tuesday started with a targeted phishing attack against a reseller for Melbourne IT, an Australian domain registrar and IT services company.
The attack resulted in hackers changing the DNS (Domain Name System) records for several domain names including nytimes.com, sharethis.com, huffingtonpost.co.uk, twitter.co.uk and twimg.com -- a domain owned by Twitter -- Jaime Blasco, director of the research lab at security firm AlienVault, said Tuesday in a blog post.
This resulted in traffic to those websites being temporarily redirected to a server under the attackers' control.
Hackers also made changes to the registration information for some of the targeted domains, including Twitter.com. However, Twitter.com itself was not impacted by the DNS hijacking attack.
A hacker group called the Syrian Electronic Army (SEA) that publicly supports Syrian President Bashar al-Assad and his government took credit for the attack via Twitter. During the past several months the group broke into the websites or Twitter accounts of several media organizations including the Financial Times, the Associated Press, The Guardian, BBC and Al Jazeera.
Initial information suggested that the systems of Melbourne IT, the company through which all of the affected domain names were registered and administered, might have been hacked. However, the company later revealed that it was one of its resellers whose account was actually compromised.
"The credentials of a Melbourne IT reseller (username and password) were used to access a reseller account on Melbourne IT's systems," Tony Smith, general manager of corporate communications at Melbourne IT, said Wednesday via email. "The DNS records of several domain names on that reseller account were changed, including nytimes.com."
The name of the reseller was not disclosed.
According to Smith, the affected DNS records have been reverted back to their original values and have been locked from further modification at the .com registry level. The .com registry and DNS zone are operated by VeriSign.
In a subsequent statement sent via email, Bruce Tonkin, the chief technology officer of Melbourne IT, revealed that the compromise was the result of a targeted phishing attack that might have affected multiple accounts.
"We have obtained a copy of the phishing email and have notified the recipients of the phishing email to update their passwords," Tonkin said Tuesday via email. "We have also temporarily suspended access to affected user accounts until passwords have been changed."
Some users likely remained affected by the attack even after the DNS records were corrected by Melbourne IT in its system, as the recursive DNS servers of their ISPs continued to serve the compromised records from cache until their time-to-live (TTL) value expired. Because of caching, DNS record changes can take up to 24 hours to propagate through the entire Internet.
DNS hijacking attacks can affect users beyond just preventing them from accessing a website, because they also allow attackers to redirect users to malicious content. According to Matthew Prince, CEO of CloudFlare, a company that provides website optimization and security services, this actually happened during this particular attack.
"Technical teams from CloudFlare, OpenDNS and Google jumped on a conference call and discovered what appeared to be malware on the site to which the NYTimes.com site was redirected," Prince said Tuesday in a blog post.
"The registrar of the primary domain the Syrian Electronic Army was using as a name server for the domains they hacked revoked the domain's registration this afternoon," he said. "Since the cache TTL on the domain was relatively short, shortly after the domain was revoked traffic largely stopped flowing to the malware infected sites."
Prince and CloudFlare did not immediately respond to an inquiry seeking more information about the type of malware that had been served during the attack.
In order to prevent rogue modification of DNS records, domain owners can ask their registrars to put registry locks in place for their domains, like Melbourne IT did for nytimes.com and the other affected websites. This lock is placed at the registry level, meaning with those companies that administer the .com, .net, .org, and other domain extensions.
"Registrars generally do not make it easy to request registry locks because they make processes like automatic renewals more difficult," Prince said. "However, if you have a domain that may be at risk, you should insist that your registrar put a registry lock in place. It's worth noting that while some of Twitter's utility domains were redirected, Twitter.com was not -- and Twitter.com has a registry lock in place."
SEA claimed Wednesday on Twitter that they hacked Melbourne IT's blog site. A message left on the site read "Hacked by SEA, Your servers security is very weak," suggesting that the hacker group might still have some level of access to Melbourne IT's systems.