The Internet Corporation for Assigned Names and Numbers (ICANN), the organization responsible for managing the Internet’s use of domain names, was recently compromised by a spear phishing campaign.

In an alert earlier this week, ICANN said it is investigating an intrusion into its networks that appears related to a spear phishing campaign in late November. Several members of ICANN’s staff received email messages that purported to have been sent from within ICANN's own domain. The email credentials of several ICANN staff members were compromised in the attack.

Those credentials were later used to gain administrative access to ICANN's Centralized Zone Data System (CZDS), ICANN said in its alert.

ICANN describes CZDS as a system that contains files containing data describing a portion of the domain space for Top Level Domains (TLDs). “Zone files contain the information needed to resolve domain names to Internet Protocol (IP) numbers,” according to ICANN. Files in the CZDS include domain names, their associated name server names, and the IP addresses for those name servers.

By gaining administrative access system, the attackers would have had access to, not just the zone files, but also information entered by users such as their names, addresses, email addresses, and phone numbers.

“Although the passwords were stored as salted cryptographic hashes, we have deactivated all CZDS passwords as a precaution,” ICANN said. The alert recommended that users of CZDS take additional measures to protect other accounts for which they might have used the same passwords.

Dan Kaminsky, chief scientist at White Ops and one of only seven individuals with the authority to recover the Internet’s root DNS keys in an emergency, said the attackers are unlikely to have been able to do much with their access.

“The reality is there's many layers of protection here, because the root -- for all its importance -- is actually really quite small,” Kaminsky said via email. “The fundamental design of DNS works by putting the least data at the point of maximum centralization. Nothing got changed in this attack, as far as we're aware of."

Attacks like this highlight the continuing danger organizations face from spear-phishing campaigns that involve the use of highly targeted emails to deliver malware. Though decidedly low-tech in approach, spear-phishing emails have proved to be one of the most effective means of delivering malware on corporate systems in recent years.

Until relatively recently, more than nine out of ten attacks involving advanced persistent threats were initiated via a spear phishing campaign. Even the mega breach at Target began with the attackers using a phishing email to steal the login credentials of a third-party vendor, which they then used to gain a foothold on Target’s network.

While spear phishing remains a major threat, there are signs that hackers have begun moving to other delivery mechanisms of late. According to security vendor Symantec, the number of spear phishing attacks per day has kept coming down steadily over the past 12 months.

In October, the average was about 45 per day, the company said. Of the attachments used in such email-based attacks, the .doc attachment type comprised 62.5 percent and .exe attachments made up 14.4 percent,” the company noted.

The companies most frequently targeted in these attacks belonged to the finance, insurance, and real estate sectors. Companies in these industries received 28% of all spear phishing emails, followed by companies in the manufacturing sector, which received about 17%, Symantec noted.