The site has since recovered after being hit yesterday by the Citadel Trojan, a form of malware that hunts for IDs and passwords.
NBC's Web site is up and running again after being knocked offline by a cyberattack for several hours yesterday.
The NBC site was the victim of a form of malware known as the Citadel Trojan. This specific strain targets companies in an attempt to steal usernames, passwords and other sensitive data. People who visit sites infected by the trojan can find their own PCs infected as well.
In the past, Citadel typically attacked banks and financial firms but has since expanded its reach to a wider range of organizations.
NBC, which is part of cable giant Comcast, is still trying to figure out how the attack occurred, a spokeswoman told Bloomberg News late yesterday. The spokeswoman, Tracy St. Pierre, said that no user data was stolen.
CNET also contacted St. Pierre for comment and will update the story if we receive additional information.
The hack caused Google to temporarly blacklist NBC.com, according to malware monitoring site Sucuri. The attack affected not only NBC's main site but related sites, such as Late Night with Jimmy Fallon and Jay Leno's Garage, Sucuri said in a blog post yesterday.
Facebook also blocked access to links to NBC as a result of the malware.
NBC is just the latest in a series of large companies hit by malware attacks.
Twitter, Tumblr, Pinterest were compromised yesterday following a security breach at Zendesk, which the three use for customer support. Apple, Facebook, Twitter were the victims of malware that may have come from Eastern Europe.
Meanwhile, the Chinese military was named as the source of a series of cyberattacks against U.S. corporations and government agencies, according to a new report by security firm Mandiant.