Exploit kits are not new to the information security community. Their popularity has increased within the underground steadily since 2006 when threat research organizations like TrendMicro began seriously tracking their growth and distribution on a global basis. Exploit kits, sometimes referred to as Exploit Packs, are essentially pre-packaged software distributions that contain malicious programs mainly used in ‘drive-by’ attacks in order to spread malware. These kits are sold in the black market within forums in the visible, deep and dark webs. Within these forums sellers market their wares to potential buyers through a variety of ways much like any software sales organization might. They tout their price, their flexibility, their ease of use. If a potential buyer can’t afford to pay for a kit outright, in many cases they will have the option to rent a kit for a given period of time for a set price. Additionally, in many instances the sellers will provide after market support features which are designed to make the over all user experience as stress free as possible. Prices range from the hundreds to thousands of dollars depending on the kit, its functionality, and its demand.

A great deal of research has been conducted on exploit kits over the years as they have continued to grow, mature, and become more widely available to the masses. In 2012 security researcher Jason Jones, then with HP DVLabs, presented on the topic at Blackhat USA Las Vegas. Jones asserted that Exploit Kits, based on his work in researching them, contained many of the following things as a general rule:

  • Installers (most of the time)
  • Exploits
  • Rarely 0-day (we’ll get there in a minute)
  • Control Panels
  • Installers
  • Statistics
  • Configurations
  • Malicious Payload Delivery Mechanisms
  • Botnets
  • Trojans
  • Fake AV

Jones presentation suggested that at the time he was conducting his research (and I’m sure his research in the years after his initial research would support this assertion) that the number of exploits associated with a given kit could be limitless if cost and availability were not an issue. His research and that of others in the space also suggested that Exploit Kits rarely if ever contained 0-day exploits. It’s important to understand that what is meant by 0-day in this context is really related to a piece of code known / proven to be able to exploit a previously undisclosed vulnerability in a given software package such as the Adobe suite for example.

Bearing in mind that Jones’ presentation was from 2012 we now fast forward to 2015 where we are seeing new trends emerge with respect to Exploit Kits in the wild. These trends are particularly interesting in that they suggest that the frequency of 0-day exploits made available in these kits is growing while the time to integrate said 0-days from the time of discovery to inclusion in the kits is shrinking rapidly.

Recent Phenomena Surrounding Exploit Kits and 0-Day Exploits

I started this blog by stating that Exploit Kits are not new to the information security community. It’s true they are not however, like much malicious code and content, they are experiencing changes at a pace not previously experienced before which makes them noteworthy. Some of these changes include the distribution of new malicious payload delivery methods. For example, the Magnitude Exploit Kit was observed distributing Cryptowall 3.0 in early 2015. We have observed an increased frequency of 0-day exploits being made available in these exploit kits, what is more the speed at which these are integrated is increasingly shorter. Several examples of this have been noted and documented within the research community. Let’s take a look at a few:

Operation Clandestine Wolf (CVE-2015-3119)

First detected by FireEye as a Service team as part of the ongoing campaigns associated with FireEye APT Group 3, Operation Clandestine Wolf was notable for the following reasons:

This particular vulnerability, Heap Based Overflow in Adobe Flash Player (CVE-2015-3115), is noteworthy largely due to the fact that it had been exploited in early June 2015, was written up in the National Vulnerability Database (NVD) on June 23, 2015 and made its way into exploit kits approximately four days later! That is an incredible rate of adoption for a recently discovered and patched vulnerability. What makes this particular case even more interesting is the demonstration of an intersection between cyber criminal and nation-state activity.

Hacking Team Adobe Flash Player Zero Day (CVE-2015-5119)

Yet another example of a 0-day vulnerability being introduced into exploit kits in a rapid time-frame is that of the Flash Player Zero Day (CVE-2015-5119) attributed to the now well-known compromise of Italian information security and surveillance technology firm Hacking Team. This case is unique in that the 0-day discovery and subsequent availability wasn’t due to the handiwork of cyber criminals looking for new ways to exploit existing systems and infrastructure to further their ends. In this instance the 0-day in question was discovered or acquired by the Italian firm in order to further their products and services to their varied clientele. At the time of this writing it is unclear who their target clientele for this weaponized code was aside from law enforcement and government entities. We’ve chosen not to speculate on their clientele in spite of the fact that there is a massive trove of data now available on the Internet related to the Hacking Team due to their breach.

The 0-day was adopted and incorporated into various exploit kits in almost record time. According some sources in as little as two days! This may have been due, in part, to the working code that was immediately available without the need for a proof-of-concept or experimentation. The following exploit kits were all observed to have incorporated the 0-day:

  • Angler Exploit Kit
  • Neutrino Exploit Kit
  • Nuclear Pack
  • Magnitude Exploit Kit

Adobe quickly released a bulletin describing their understanding of the vulnerability and their recommendation for remediation of it. It should be noted that there have been reports that the source code stolen during the breach of Hacking Team related to this 0-day may have been used to develop tools used in attacks observed by TrendMicro in Korea and Japan prior to the breach of Hacking Team which suggests that someone with access to their source code used it to create a derivative of the weaponized code. Additionally, both the teams at FireEye Labs and Palo Alto Networks Unit 42 have verified that the APT group 3 (aka UPS) have incorporated this 0-day code into spear phishing campaigns targeting United States government entities.

Hacking Team Adobe Flash Player Zero Day (CVE-2015-5122 & CVE-2015-5123)

On Friday July 10, 2015 the team at FireEye Labs identified a Proof of Concept (PoC) for two more Adobe Flash Player Zero Day exploits (CVE-2015-5122 & CVE-2015-5123) found within the cache of data divulged by threat actors as part of the Hacking Team breach. At least one source as of Saturday July 11, 2015 stated that the 0-day has been observed having been introduced and within at least one high profile exploit kit. The exploit kit in question is that the 0-day was introduced to is the:

  • Angler Exploit Kit

The Adobe team was notified and issued a release dedicated to these 0-days however at the time of this writing the national vulnerability database has yet to update its records to include the vulnerabilities.


Exploit kits are, and remain, a staple of a variety of threat actors the world over. Their popularity is growing and will continue to grow so long as their authors continue to satisfy the needs of their current and potential clients by providing the latest advances in features, functionality, and access to 0-day exploits. This should be concerning to everyone tasked with securing an enterprise environment, or with researching the threat landscape. We should worry because of the severity of the exploits recently observed and their rapid adoption and advancement within these exploit kits.

So, what can the defender do to prevent adversaries from using exploit kits against their user populations or their home users? For starters, they can stay focused and educated with respect to what is occurring within the threat landscape and how it may impact them based on their digital footprints. This is important for several reasons not the least of which is that it will enable the defender to take pre-emptive actions (e.g. education, patching, updating of IDS / IPS signatures and firewall rules etc.) in mitigating their risks.

As ever, patching, as part of that defense strategy will remain a critical function of the defender; to fail to patch is to open the door wide for the adversary. Additionally, defenders may wish to explore advancements taking place within the realm of anti-virus and end point protection technologies. Many organizations are making great strides in providing more advanced, less signature-dependent technologies available to both enterprise and consumer clients alike. Finally, diligence will be key in mitigating the risks presented by Exploit Kits armed with recently patched 0-day exploits. We can’t defend against that of which we’re unaware, so diligence will be key.