Welcome!

Cloud Security Authors: Peter Galvin, Sanjay Zalavadia, Elizabeth White, Liz McMillan, Stefano Stabellini

Related Topics: Cloud Security

Cloud Security: Blog Post

Malware Delivery – Understanding Multiple Stage Malware

How trusted file attachments has opened the vector for continued intrusions.

To some of us, seeing an email with malware embedded in a PDF, Word or Excel attachment is common. In fact, it has become the new norm for malware delivery to use file types that are not obviously malicious (versus something like a .exe). Gone are the days of wide-open acceptance of all file extensions for attachments within an email. In today's network defense-in-depth techniques, one of the layers is naturally email security. This includes the scrutinizing of emails for embedded links or attachments that could be potentially malicious, scanning attachments for possible detectable viruses and even inspecting the mail header for details that could point to the continued use of a particular "sender" address targeting an organization.

With the delivery of the malware always evolving to avoid being detected, why is it so common to see multi-stage malware? What exactly IS multi-stage malware, and why can it be more difficult to detect through common defense-in-depth strategies? I recently sat with a customer who ran these questions by me.  They were concerned that this might be some kind of new and sophisticated attack being used against their organization that their security team was not aware of. Truth is, this type of attack method is more common than you know, and has been going on for a significant period of time.

Let's start by tackling the easiest questions.

Question: What is multi-stage malware?

Answer: It is malware that is delivered in stages.  Seriously, that's it.

Question: So then what are the stages?

Answer: Ah, I was hoping that was your next question...

The typical stages for the delivery are as follows;

Stage 1: The main goal of the first stage is to simply get some kind of execution on a victim computer to retrieve the larger portion of the malware.  Utilizing a legitimate looking file (PDF, DOC, XLS) that is embedded with the stage 1 malware, the attacker can entice the target to open it, and allow execution. After execution, the first stage malware may also find some way to make itself persistent. What do I mean by persistent? Well let's say that as soon as you open an infected PDF, the stage 1 malware begins execution on your computer, but you happen to immediately shut down your computer.  If that malware did not create some kind of way to re-execute after you start your computer, it will not execute again until you open the infected PDF again. Attackers know that it's unlikely you will re-open the attachment, so they like to build in a way for the malware to re-execute after your computer starts up.  That way it is guaranteed to finish its initial job, which is to retrieve the next stage malware.

Stage2: This is where the more robust malware sections of the malware are introduced, potentially causing an unfettered amount of damage to its victim computer. Stage 2 typically gives the attacker an array of capabilities that are not available with stage 1, such as:

  • Victim computer screen capture
  • Start webcam
  • Graphical ability to browse victim computer file system
  • Stealing of files and software
  • Deletion of files
  • Elevation or escalation of privileges
  • Keylogging and potential destruction of the victim file system

Furthermore, Stage 2 malware may also provide the ability for the attacker to migrate to another computer on the same network which provides the ability for even more extensive damage by allowing the attacker to spread out and cause an increase in damage.

Question: Are those the only stages of delivery?

Answer: Not always, but this is the most common.  Sometimes "plugins" or "modules" are available to add to the malware, and they can be delivered or removed on an as needed basis.  The attacker wants to limit the amount of network traffic to a particular domain that is hosting malware as this could lead to detection and blocking, which would stop the potential for successful delivery of any future malware or even stage 2.

Question: Why stage the delivery at all?  Why not just embed all of the malware instead of a portion in the infected document or file?

Answer: There are a few reasons for staging the delivery, one of them being size. Simply put, if the size of the malware is large enough then embedding the whole thing into a PDF would make the file quite large; therefore, more suspicious.  Another reason is to limit the possibility of detection through various scanners and traffic inspectors. The first stage of the malware is quite light in what commands and system calls that it makes which helps to evade detection by signature or even heuristics. It is not uncommon at all to see a PDF reader software open a PDF, then immediately connect to the Internet. Most PDF readers routinely check for updates as soon as they are opened, and attackers know this to be true often enough.  So the stage 1 malware just hides within that behavior, reducing its ability to be detected. Lastly, development of custom malware is expensive and takes time, so losing the entire piece of malware due to detection of any sort can be a huge set back to the attackers. Even if the attackers are using commercial or open source attack tools, rebuilding them to avoid antivirus detection can be time consuming and costly. Losing the stage 1 malware through  detection is easier to address than burning the complete malware package. By staging the delivery it limits the potential loss to the attacker. There many other reasons to break the malware up and retrieve upon infection, but these are some of the most important ones.

Question: This is making more and more sense to me, but just quickly can you go over why it's much harder to detect?

Answer: The smaller and more embedded the malware is, the more difficult to detect, especially inside of a commonly used and trusted file. When the commands for the malware are simplified as well as the needs from a victim computer to execute, again, detection is difficult. When malware is overly complicated, or it has large consumption requirements from the operating system to correctly function, the chances for detection though defense-in-depth techniques is increased. Large, complicated malware is more likely to break and alert the user to its presence, or even get detected by antivirus. It is also most likely to fail Deep Packet Inspection at the IDS/IPS layer due to possible signatures for specific system calls the malware makes. Small, simple malware finds a home inside of the most common files and documents that we not only use and open every day, but also are typically allowable as an attachment in an email. Because the malware is small, it can be easily modified, making signature development almost impossible. Breaking the malware apart also changes which security tools are inspecting the malware. If stage 1 is delivered through an email, than you will have to get through an IDS/IPS, an Email AntiVirus product (if you are dealing with an enterprise), as well as any attachment inspection that occurs on the email gateway. Stage 2 is then delivered after successful infection of victim computer, typically after the victim computer asks a particular web server for the stage 2 malware. If this request is done over SSL/HTTPS, then there is a good chance there will be no inspection of the malware until it reaches the host.  At delivery, the malware has to contend with antivirus on the victim computer, which is trivial for a sophisticated attacker to either bypass or defeat.

Question: If it's so damn hard to detect, how on earth do I stop it?

Answer: Excellent question, this is something we can address in my next blog, "Better Host Based Protection, Logically".

More Stories By Cory Marchand

Cory Marchand is a trusted subject matter expert on topics of Cyber Security Threats, Network and Host based Assessment and Computer Forensics. Mr. Marchand has supported several customers over his 10+ years within the field of Computer Security including State, Federal and Military Government as well as the Private sector. Mr. Marchand holds several industry related certificates including CISSP, EnCE, GSEC, GCIA, GCIH, GREM, GSNA and CEH.

@ThingsExpo Stories
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...
There are several IoTs: the Industrial Internet, Consumer Wearables, Wearables and Healthcare, Supply Chains, and the movement toward Smart Grids, Cities, Regions, and Nations. There are competing communications standards every step of the way, a bewildering array of sensors and devices, and an entire world of competing data analytics platforms. To some this appears to be chaos. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Bradley Holt, Developer Advocate a...
Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, wh...
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
SYS-CON Events announced today that Bsquare has been named “Silver Sponsor” of SYS-CON's @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. For more than two decades, Bsquare has helped its customers extract business value from a broad array of physical assets by making them intelligent, connecting them, and using the data they generate to optimize business processes.
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
There is little doubt that Big Data solutions will have an increasing role in the Enterprise IT mainstream over time. Big Data at Cloud Expo - to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA - has announced its Call for Papers is open. Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is...
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, discussed how research has demonstrated the value of Machine Learning in delivering next generation analytics to imp...
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
The cloud market growth today is largely in public clouds. While there is a lot of spend in IT departments in virtualization, these aren’t yet translating into a true “cloud” experience within the enterprise. What is stopping the growth of the “private cloud” market? In his general session at 18th Cloud Expo, Nara Rajagopalan, CEO of Accelerite, explored the challenges in deploying, managing, and getting adoption for a private cloud within an enterprise. What are the key differences between wh...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo Silicon Valley Call for Papers is now open.
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his Day 2 Keynote at @ThingsExpo, Henrik Kenani Dahlgren, Portfolio Marketing Manager at Ericsson, discussed how to plan to cooperate, partner, and form lasting all-star teams to change t...
Connected devices and the industrial internet are growing exponentially every year with Cisco expecting 50 billion devices to be in operation by 2020. In this period of growth, location-based insights are becoming invaluable to many businesses as they adopt new connected technologies. Knowing when and where these devices connect from is critical for a number of scenarios in supply chain management, disaster management, emergency response, M2M, location marketing and more. In his session at @Th...
SYS-CON Events announced today that ReadyTalk, a leading provider of online conferencing and webinar services, has been named Vendor Presentation Sponsor at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. ReadyTalk delivers audio and web conferencing services that inspire collaboration and enable the Future of Work for today’s increasingly digital and mobile workforce. By combining intuitive, innovative tec...
Amazon has gradually rolled out parts of its IoT offerings, but these are just the tip of the iceberg. In addition to optimizing their backend AWS offerings, Amazon is laying the ground work to be a major force in IoT - especially in the connected home and office. In his session at @ThingsExpo, Chris Kocher, founder and managing director of Grey Heron, explained how Amazon is extending its reach to become a major force in IoT by building on its dominant cloud IoT platform, its Dash Button strat...
industrial company for a multi-year contract initially valued at over $4.0 million. In addition to DataV software, Bsquare will also provide comprehensive systems integration, support and maintenance services. DataV leverages advanced data analytics, predictive reasoning, data-driven diagnostics, and automated orchestration of remediation actions in order to improve asset uptime while reducing service and warranty costs.
Vidyo, Inc., has joined the Alliance for Open Media. The Alliance for Open Media is a non-profit organization working to define and develop media technologies that address the need for an open standard for video compression and delivery over the web. As a member of the Alliance, Vidyo will collaborate with industry leaders in pursuit of an open and royalty-free AOMedia Video codec, AV1. Vidyo’s contributions to the organization will bring to bear its long history of expertise in codec technolo...