The Zeus crimeware toolkit lives on. Since its developer reportedly bequeathed the application's code base to rival SpyEye in October 2010, security researchers have been watching for a hybrid toolkit to emerge.
Now, it's apparently arrived. "We've acquired a sample of version 1.3.05 of the SpyEye builder, which appears to be the result of … said merger," a recent online post from Trend Micro senior threat researcher Loucif Kharouni stated.
Kharouni said the application combines disparate features from previous versions of the two crimeware toolkits. For example, whereas Zeus required buyers to include desired plug-ins from the get-go, SpyEye allowed users to install them after the purchase. Now, the new software will offer some of the plug-in functionality of the former, with the "buy when you like" functionality of the latter.
Of course, a botnet is only as good as its ecosystem of compromised -- aka zombie -- PCs. Here, the hybrid toolkit could be a bigger threat than its predecessors. "The merger of Zeus and SpyEye is significant because it not only puts together two different code bases, but it is also merging two different bot networks, meaning 'SpyZeus' will have a much greater reach," Anup Ghosh, chief scientist of virtual browser protection vendor Invincea, said in an email. "Essentially SpyEye is subsuming the Zeus Trojan kit, network, and user base."
Other features of the new SpyEye include assessments of whether Web injection attacks will work against Firefox, plus better plug-in control and browser cookie clearing. Plug-in options include the ability to steal certificates from Windows cryptographic storage, a tool for faking HTTP and HTTPS Web pages in IE and Firefox -- without having to connect to the original Web server -- as well as an FTP back door and bug reporter.
According to Trend Micro, SpyEye also actively attempts to evade or disable Rapport, a free secure-browsing tool from Trusteer with a user base numbering in the millions. About 70 financial services institutions also actively push the software to their customers.
Of course, targeting isn't the same as disabling. In the wake of the Trend Micro analysis, Trusteer revealed that Zeus has been targeting Rapport for some time, which is information it's shared with business partners, but not the general public or competitors. "Zeus has been launching direct attacks against Trusteer for the last couple of years now. There are several different attacks against Rapport incorporated into different versions of Zeus, all of which focus on disabling the software on customer computers. All are successfully blocked by Trusteer," Mickey Boodaei, CEO of Trusteer, said in an email.
In fact, he said that the attack code essentially gives itself away, making it easy to find and eliminate, when it gets hostile and attempts to terminate certain threads -- such as the Rapport thread responsible for blocking HTML injection -- or outright delete files associated with security applications. "It seems to me that in their passion to differentiate service from other malware tools, the authors of SpyEye ignored a simple rule -- for malware it's always better to keep a low profile," Boodaei said.