Not long ago, miscreants who wanted to buy an exploit kit — automated software that helps booby-trap hacked sites to deploy malicious code — had to be fairly well-connected, or at least have access to semi-private underground forums. These days, some exploit kit makers are brazenly advertising and offering their services out in the open, marketing their wares as browser vulnerability “stress-test platforms.”
Aptly named after the river in Greek mythology that separates mere mortals from the underworld, the Styx exploit pack is a high-end software package that is made for the underground but marketed and serviced at the public styx-crypt[dot]com. The purveyors of this malware-as-a-service also have made a 24 hour virtual help desk available to paying customers.
Styx customers might expect such niceties for the $3,000 price tag that accompanies this kit. A source with access to one Styx kit exploit panel that was apparently licensed by a team of bad guys shared a glimpse into their operations and the workings of this relatively slick crimeware offering.
The Styx panel I examined is set up for use by a dozen separate user accounts, each of which appears to be leveraging the pack to load malware components that target different moneymaking schemes. The account named “admin,” for example, is spreading an executable file that tries to install the Reveton ransomware.
Other user accounts appear to be targeting victims in specific countries. For example, the user accounts “IT” and “IT2” are pushing variants of the ZeuS banking trojan, and according to this Styx panel’s statistics page, Italy was by far the largest source of traffic to the malicious domains used by these two accounts. Additional apparently country-focused accounts included “NL,” AUSS,” and “Adultamer” (“amer” is a derisive Russian slur used to describe Americans).
An exploit kit — also called an “exploit pack” (Styx is marketed as “Styx Pack”) is a software toolkit that gets injected into hacked or malicious sites, allowing the attacker to foist a kitchen sink full of browser exploits on visitors. Those visiting such sites with outdated browser plugins may have malware silently installed.
Unlike other kits, Styx doesn’t give a detailed breakdown of the exploits used in the panel. Rather, the panel I looked at referred to its bundled exploits by simple two-digit numbers. This particular Styx installation used just four browser exploits, all but one of which targets recent vulnerabilities in Java. The kit referred to each exploit merely by the numbers 11, 12, 13 and 32.
According to the considerable legwork done by Kafeine, a security blogger who digs deeply into exploit kit activity, Styx Kit exploit #11 is likely to be CVE-2013-1493, a critical flaw in a Java browser plugin that Java maker Oracle fixed with an emergency patch in March 2013. Exploit 12 is almost certainly CVE-2013-2423, another critical Java bug that Oracle patched in April 2013. In an instant message chat, Kafeine says exploit #13 is probably CVE-2013-0422, a critical Java vulnerability that was patched in January 2013. The final exploit used by the kit I examined, number 32, maps to CVE-2011-3402, the same Microsoft Windows font flaw exploited by the Duqu Trojan.
The Styx stats page reports that the hacked and malicious sites used by this kit have been able to infect roughly one out of every 10 users who visited the sites. This particular Styx installation was set up on June 24, 2013, and since that time it has infected approximately 13,300 Windows PCs — all via just those four vulnerabilities (but mostly the Java bugs).
One very interesting pattern I observed in poking at this exploit pack — and 0thers recently — is the decreasing prevalence or complete absence of reported infections from Google Chrome users, and to a lesser extent users of recent versions of Mozilla Firefox. As we can see from the graphic at the top of this blog post, users browsing with Microsoft’s Internet Explorer made up the lion’s share of victims.
This Styx installation reports installing malware on systems of just a handful of Firefox users, and against not a single Chrome user. In fact, the author of this kit freely states in a Q&A from an underground forum sales thread that his kit doesn’t even work against Chrome. For a complete breakdown of victims by browser and operating system, see this graphic.
Kafeine said he, too, has noticed a pronounced shift in the browser breakdowns from different exploit kits.
“Not many exploit kits [perform] very well against Chrome,” Kafeine said, noting that both Chrome and Firefox both now include integrated PDF readers, and that exploits against Adobe’s PDF reader have traditionally been a key contributor to exploit kit infection statistics.
Kafeine said one malware gang whose work he has followed — an organized crime crew that uses the Gameover ZeuS variant — doesn’t even attempt to infect Chrome users who wander into its malware traps. Instead, those users are hit with a social engineering attack that tries to trick them into installing the malware by disguising it as a Chrome browser update.
“Those users are automatically redirected to a fake Chrome update page,” Kafeine said.
For more details on Styx and the different flavors of this exploit kit that have emerged in recent months, check out these blog posts:
Styx Exploit Kit Takes Advantage of Vulnerabilities
Styx Exploit Kit Analysis – Building a Bridge to the Underworld
Crossing the Styx
A “Styxy” Cool EK!