"At 16:43 CET [12:43 EST] this afternoon we noticed that the NBC.com website links to the redkit exploit kit that is spreading Citadel malware, targeting U.S. financials (sic) institutions," warned security analyst Barry Weymes at Dutch security firm Fox-IT in a Thursday blog post. "This version of Citadel is only recognizable by 3 out of the 46 antivirus programs on virustotal.com."
Malware-spewing NBC websites included the sites for Late Night with Jimmy Fallon and Jay Leno's Garage, according to a blog posted by Tony Perez, COO of security software vendor Sucuri.
In short order, Google was blocking some NBC websites from search results, warning that they appeared to be infected with malware. While some reports suggested that NBC expunged the malware after just 15 minutes, multiple security researchers reported that the infections persisted for at least four hours.
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Attackers appeared to have compromised the NBC websites using the RedKit attack toolkit, which then targeted users with attacks designed to exploit vulnerabilities in their Java browser plug-in, or Adobe Reader. The remotely exploitable Java bug (CVE-2013-0422) being targeted was discovered in January and patched last month. Meanwhile, the malicious PDF file served up by the malware was recognized Friday morning by only six out of 46 antivirus software packages, according to VirusTotal. Initial reports on the attack from security researchers didn't disclose if the Adobe Reader bug was a zero-day flaw, or previously discovered bug.
The iframe used in the attack called on an ever-changing list of external URLs to load attack code. "This tells us that something on the server is generating the payload," said Sucuri's Perez in his Thursday blog post. "This isn't an uncommon practice, it also tells us that the script is likely still on the box. The fact that it's impacting other sites tells us that the compromise might extend beyond the Web application and onto the server. If those other sites are stored on separate boxes then we're looking at a much bigger, network, compromise, but that is speculative at the moment."
By infecting a high-profile site such as NBC.com, which is one of the top 600 most popular sites in the United States, attackers had the opportunity to quickly infect numerous visitors. "Targeting media and news websites can vastly improve an attacker's chances of success," according to Fox-IT's Weymes, which was one of the first organizations to spot the attack. "Users presume these large organizations' websites to be free from malware. If an attacker can gain access to these Web servers, they can use them to distribute malware to every visitor of that Web server."
Attackers made the most of their exploit window, using RedKit to target PCs with up to three different exploit kits, including the Citadel crimeware toolkit, which is designed to steal financial information. According to Fox-IT, the attackers were targeting account details for numerous U.S. financial institutions, including American Express, Bank of America, Chase, Citibank, Citizensbank Online, Fifth Third Bank, Navy Federal Credit Union, PNC, Schwab, Suntrust, TD Ameritrade, USAA and Wells Fargo.
The drive-by NBC website attacks also infected some visitors with ZeroAccess malware, which is used to launch clickjacking attacks that generate fake pay-per-click revenues for botnet controllers or their clients. "ZeroAccess is a dangerous threat that uses stealth techniques in order to hinder its detection and removal," said SurfRight security researcher Erik Loman in a blog post.
RedKit served up a third piece of malware which has yet to be identified. "Some antivirus vendors identify this malware as Zbot or a rootkit ... but it is most definitely not Zbot and it's not a rootkit either," Loman said. "The malware binary has a curious name at the end 'SadokBdi,'" which may connect it to previously seen malware known as "Sadok."
The timing of the high-profile NBC attack may be tied to Oracle and Adobe having recently released patches for multiple critical vulnerabilities in Java, Reader and Acrobat. Once vendors release a patch, criminals often reverse-engineer the fix to reveal the underlying vulnerability, which they then begin targeting. Anyone who doesn't quickly update their software thus remains highly vulnerable to having their PC compromised by an attacker, which can lead to their personal financial account information being stolen, keystrokes recorded and their PC being made to serve as part of a botnet.
Owing to many users failing to update the Java Runtime Environment installed on their PCs, Java bugs in particular remain quite popular with -- and effective for -- attackers.