Finjan Uncovers Insidious New Variant of Crimeware Toolkit Infecting More Than 10,000 US Websites

In its just-released Malicious Page of the Month report, Finjan explores the ìrandom js toolkit,î the latest example in the trend among cybercriminals to undermine ëtrustedí web sites

Finjan Inc., today announced that its Malicious Code Research Center (MCRC) has identified yet another significant new web attack -- the latest in a genre of crimeware that threatens to turn highly trusted web sites into insidious traps for unwary visitors. More than 10,000 websites in the US were infected in December by this latest malware. The attack, which Finjan has designated ìrandom js toolkit,î is an extremely elusive crimeware Trojan that infects an end userís machine and sends data from the machine via the Internet to the Trojan's ìmasterî, a cybercriminal. Data stolen by the Trojan can include documents, passwords, surfing habitats, or any other sensitive information of interest to the criminal.

The random js toolkit was detected using Finjanís patented real-time code inspection technology while diagnosing usersí web traffic during December 2007. The attack is described in detail in Finjanís latest ìMalicious Page of the Monthî report released today. The report explores the new attack vector in depth, providing an illustration of the attack in action, as captured ìin the wildî; an analysis of the effectiveness of its evasive techniques; examples of high-ranked and trusted domains that were compromised by this attack technique; and an analysis of a successful exploitation. To download the report, visit www.finjan.com

The random js toolkit is a JavaScript code that is created dynamically and changes every time it is being accessed. As a result, it is almost impossible to be detected by traditional signature-based anti-malware products. Explained Finjan CTO Yuval Ben-Itzhak, ìSignaturing a dynamic script is not effective. Signaturing the exploiting code itself is also not effective, since these exploits are changing continually to stay ahead of current zero-day threats and available patches. Keeping an up-to-date list of ëhighly-trusted-doubtfulí domains serves only as a limited defense against this attack vector.î

ìWhatís needed to counter this exploit is dynamic code inspection technology that can detect and block an attack in real time,î Ben-Itzhak said. ìThis technology doesnít depend on the origin URL, signature or the siteís reputation, but inspects the Web content in real-time, as served. It analyzes the codeís intentions before enabling it be executed on the end-user browser.î

Over 30,000 new infected web pages are being created every day
Ben-Itzhak noted that the random js toolkit is an example of the recent trend among cybercriminals to undermine ëtrustedí web sites. ìIn mid-year 2007, studies showed there were nearly 30,000 new infected web pages being created every day. About 80 percent of those pages hosting malicious software or containing drive-by downloads with damaging content were located on hacked legitimate sites. Today the situation is much worse.î

The random js attack is performed by dynamic embedding of scripts into a webpage. It provides a random filename that can only be accessed once. This dynamic embedding is done in such a selective manner that when a user has received a page with the embedded malicious script once, it will not be referenced again on further requests. This method prevents detection of the malware in later forensic analyses.

Finjanís research into the random js toolkit found that around 10,000 legitimate domains served the malicious code in December. Among the infected web sites, Finjan identified highly trusted domains. Finjan alerted administrators of both sites, and the malicious code was subsequently removed from the sites and is no longer active.