Since its introduction in early 2016 and throughout this year, the distribution of the Locky ransomware has been overwhelmingly facilitated by attached script applications written in JScript or Visual Basic. These script applications have been delivered as the content of an attached archive such as a Zip or RAR file delivered as part of the email messages.

It seems that each time the information security community is ready to declare the Locky ransomware dead and gone, phishing threat actors launch new campaigns with new characteristics.

Locky’s presence on the threat landscape dates back to February 2016 when this malware formalized and matured the ransomware business model in phishing emails. Coupled with a tenacious distribution strategy, Locky dominated the phishing markets throughout 2016. Since early 2017, Locky’s presence on the threat landscape has been far more tepid. Its subdued presence on the threat landscape and intermittent distributions led to rumors that Locky was a thing of the past; many people were surprised when new Locky distributions took place. However, it is clear that despite a smaller degree of tenacity in deployment, the criminals using the Locky ransomware still see benefit from its use. And incremental changes in behavior indicate that these criminals are investing in future use, as well.

The most recent iterations of Locky distributions have replayed some of the simplest techniques for this malware’s distribution in phishing emails. The lures used in these phishing emails make vague references to document delivery, unpaid invoices, received voice mails, or receipts for payments, all examples of content used prolifically in the distribution of ransomware and other malware tools. Some standout examples demonstrate the compelling, yet vague messaging used to deliver this destructive malware.

Figure 1 – Locky phishing emails leverage vague, yet compelling narratives

While attackers continue to use similar phishing emails, the most recent Locky binaries demonstrate that small, incremental changes to the malware’s behavior are being implemented. These changes are mostly superficial but serve to break from expected norms in small ways. The first change, and likely the one to garner the most attention, was the use of two new file extensions applied to files encrypted by the ransomware. Previous iterations of Locky deployments have used extensions ranging from the sensible “.locky” to the more esoteric “.osiris”, “.odin”, and “.aesir” extensions.

In the past two weeks, two new, distinctive extensions have been used. The first, “.diablo6”, evokes a more intimidating ethos for the ransomware. Other samples use “.lukitus”, likely evoking the Finnish word for “locking.” Additionally, a more significant modification comes in the command and control callback resources leveraged by the ransomware to report new infections.

One of the simplest techniques for identifying a malware variety and its communications is to match suspicious traffic to known resource paths used by that malware. For many Locky samples in 2017, command and control resources could be identified by the presence of a “/checkupdate” callback URI path. However, this has also been replaced in recent samples that apply the “.lukitus” encrypted file extension by a “/imageload.cgi” resource path. For very tightly-tuned detection schemes, this change could result in the latter being categorized incorrectly because it represents a departure from the established norm for this malware.

Figure 2 – Small changes to command and control callback destination

Despite the numerous stories about Locky “comebacks,” each additional return to prominence serves as a reminder that the Locky ransomware and the business model it supports is a valuable monetary strategy for threat actors. As a result, it is unlikely that Locky will be fully unseated as a premier ransomware tool until a truly superior replacement emerges. Until then, it is imperative that network defenders and information security professionals continue to leverage intelligence on the behavior, techniques, and modifications exhibited by criminals deploying the Locky ransomware.

Use PhishMe® to condition your employees to recognize, report, and respond to these growing threats.

One core element of the information security mission is the successful assessment of the risk posed to an organization by a malware sample or malware variety delivered by a phishing email. In 2017, phishers have embraced the use of adaptable and flexible malware to gain initial footholds in a network before monetizing the infected host. The intersection of these two missions creates a scenario in which open-ended, adaptable botnet malware challenges information security professionals to prepare for a wide array of malware capabilities–in some case without much insight into the real risks posed by a malware tool.

However, in some cases a malware tool can reveal most, if not all, of its capabilities in a way that helps an organization identify malware risks. The Zeus Panda botnet malware is one of the more popular malware tools this year, and its use has been documented in numerous phishing attacks. It wholly embodies the principles of a multipurpose botnet tool by providing threat actors with a number of avenues for monetizing infected hosts. The tenacity and creativity with which threat actors have delivered this malware makes it a prominent constituent of the threat landscape but with limited expressions of its capabilities. Yet, understanding those capabilities is crucial for network defenders to understand the impact this malware can have within a protected environment.

Through analysis of behavior exhibited by Zeus Panda samples, PhishMe researchers uncovered a comprehensive assessment of this botnet tool’s capabilities. These capabilities were described through a list of module commands to either execute a task or update a module to support enhanced capabilities. The list below lists some operations for these modules.

Figure 1 – Zeus Panda modules provide a great deal of information about its capabilities

These module execution and update references can be interpreted as a guide to the capabilities of the Zeus Panda malware. For example, “grab2 user_cookies_get” and “grab2 user_passes_get” both imply that information stored in a browser cookie cache or password safe may be available to the “grab2” module. This could provide an avenue for threat actors to steal browser-session data or passwords for reuse. Similarly, the “info” module may provide reconnaissance about infected environments via the collection of information about the infected host. This information can be in turn leveraged in conjunction with the “user_execute” command to customize an attack through the deployment of a more specialized malware tool.

Other available modules–“klog”, “pony”, and “socks”–imply keylogger, Pony information stealer, and SOCKS proxy capabilities are available to the threat actor. Each of these would greatly enhance the threat actor’s insight into victim activity, stored passwords and credential data, and the ability to abuse the infected machine as a network proxy or traffic relay respectively. Additionally, a series of VNC modules would give the threat actor an option for full remote control of infected hosts.

Each of these elements from this brief list of module execution and update operations can be used to provide network defenders and information security professionals with an assessment of the risks posed by Zeus Panda. Furthermore, if a sample of this malware is present within a protected environment, comparing network communications and endpoint artifacts with this list of capabilities can help in the response process as well.

As malware creators and phishing threat actors further commoditize malware tools to maximize their opportunities and options regarding infected hosts, collecting intelligence on the capabilities available to those threat actors becomes increasingly important. A comprehensive defense strategy must include response plans and anticipatory defenses to limit a malware’s impact as well as prevent its successful deployment. The first step is empowering email users to recognize phishing techniques and report suspicious emails. Beyond this crucial first step, responders must be empowered to understand the risks posed by the malware these emails deliver to better defend the enterprise.

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