SAN FRANCISCO — Security experts have found a network of 74,000 virus-infected computers that stole information from inside corporations and government agencies.
The unusual thing about the incident is not that it happened, but that it was discovered, and it is a reminder of the dangers of having computers with sensitive data connected to the Internet.
More than 2,400 organizations — including financial institutions, energy companies and federal agencies — were infiltrated by the "botnet," according to the NetWitness Corp. security firm, which discovered it.
NetWitness didn't name the companies or agencies whose computers were compromised. The Wall Street Journal said the affected companies included Merck & Co., Cardinal Health, Paramount Pictures and Juniper Networks Inc. Merck and Cardinal Health said in statements Thursday that one computer in each company was among those in the botnet, but no sensitive information was taken. The other two companies didn't return messages seeking comment Thursday.
"This kind of stuff is out there and it's pervasive," said Amit Yoran, chief executive of NetWitness and former cybersecurity chief at the Homeland Security Department. Parts of the botnet discovered by his firm likely are still active. He said the network appears to be run from computers in Eastern Europe and China, but it's not certain the perpetrators are there.
Botnets are networks of poisoned PCs that are remotely controlled by hackers and behave like their criminal robots. The PCs are often infected when their owners visit bad Web sites or open malicious e-mail attachments.
Botnets are a major tool for cybercrime that help criminals amass troves of stolen data that they can sell on the black market or use for their own schemes, such as yanking money from victims' bank accounts.
The botnet NetWitness discovered used malicious software called "ZeuS" that steals passwords and other online credentials. It's primarily focused on poaching Internet banking credentials and is well known in the security community.
Security experts who weren't part of the NetWitness report said the findings illustrate the growing risk from the ZeuS software, whose authors are constantly updating it to evade detection by antivirus software and other security measures.
Don Jackson, a researcher with the counter threat unit of SecureWorks, said the botnet that NetWitness found was a "major threat" but said a bigger concern is a new version of ZeuS that has appeared in the past few months and is more powerful and even harder to detect.
One of its features is that it gives a hacker the ability to conduct financial transactions directly from a compromised computer. Otherwise, the criminal would have to steal the login credentials and use them on another computer. Some banks have put up extra security measures to detect and stop that.