Welcome!

Cloud Security Authors: Liz McMillan, Pat Romanski, Elizabeth White, Ravi Rajamiyer, Ed Featherston

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
We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA
The hot topics in the industry today seem to center around Digital Transformation and Mobile Apps. While a digital transformation strategy is crucial to keep up with the chaos in your industry, customer demands, and other disruptions, the need to create mobile apps to remain relevant in your market and to your customers is equally a no-brainer. Regardless of the approach, the next question always seems to pop up: What architecture should I chose? Native? Hybrid? Managed? Hosted?
Multiple data types are pouring into IoT deployments. Data is coming in small packages as well as enormous files and data streams of many sizes. Widespread use of mobile devices adds to the total. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists will look at the tools and environments that are being put to use in IoT deployments, as well as the team skills a modern enterprise IT shop needs to keep things running, get a handle on all this data, and deli...
SYS-CON Events announced today that EARP Integration will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. EARP Integration is a passionate software house. Since its inception in 2009 the company successfully delivers smart solutions for cities and factories that start their digital transformation. EARP provides bespoke solutions like, for example, advanced enterprise portals, business intelligence systems an...
The 21st International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Machine Learning 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 busin...
New competitors, disruptive technologies, and growing expectations are pushing every business to both adopt and deliver new digital services. This ‘Digital Transformation’ demands rapid delivery and continuous iteration of new competitive services via multiple channels, which in turn demands new service delivery techniques – including DevOps. In this power panel at @DevOpsSummit 20th Cloud Expo, moderated by DevOps Conference Co-Chair Andi Mann, panelists will examine how DevOps helps to meet th...
SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.
SYS-CON Events announced today that Ocean9will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Ocean9 provides cloud services for Backup, Disaster Recovery (DRaaS) and instant Innovation, and redefines enterprise infrastructure with its cloud native subscription offerings for mission critical SAP workloads.
SYS-CON Events announced today that T-Mobile will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. As America's Un-carrier, T-Mobile US, Inc., is redefining the way consumers and businesses buy wireless services through leading product and service innovation. The Company's advanced nationwide 4G LTE network delivers outstanding wireless experiences to 67.4 million customers who are unwilling to compromise on ...
SYS-CON Events announced today that CollabNet, a global leader in enterprise software development, release automation and DevOps solutions, will be a Bronze Sponsor of SYS-CON's 20th International Cloud Expo®, taking place from June 6-8, 2017, at the Javits Center in New York City, NY. CollabNet offers a broad range of solutions with the mission of helping modern organizations deliver quality software at speed. The company’s latest innovation, the DevOps Lifecycle Manager (DLM), supports Value S...
SYS-CON Events announced today that Hitachi Data Systems, a wholly owned subsidiary of Hitachi LTD., will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City. Hitachi Data Systems (HDS) will be featuring the Hitachi Content Platform (HCP) portfolio. This is the industry’s only offering that allows organizations to bring together object storage, file sync and share, cloud storage gateways, and sophisticated search and...
SYS-CON Events announced today that delaPlex will exhibit at SYS-CON's @CloudExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. delaPlex pioneered Software Development as a Service (SDaaS), which provides scalable resources to build, test, and deploy software. It’s a fast and more reliable way to develop a new product or expand your in-house team.
SYS-CON Events announced today that Progress, a global leader in application development, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Enterprises today are rapidly adopting the cloud, while continuing to retain business-critical/sensitive data inside the firewall. This is creating two separate data silos – one inside the firewall and the other outside the firewall. Cloud ISVs oft...
SYS-CON Events announced today that Peak 10, Inc., a national IT infrastructure and cloud services provider, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Peak 10 provides reliable, tailored data center and network services, cloud and managed services. Its solutions are designed to scale and adapt to customers’ changing business needs, enabling them to lower costs, improve performance and focus intern...
SYS-CON Events announced today that Cloud Academy will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud computing technologies. Ge...
Existing Big Data solutions are mainly focused on the discovery and analysis of data. The solutions are scalable and highly available but tedious when swapping in and swapping out occurs in disarray and thrashing takes place. The resolution for thrashing through machine learning algorithms and support nomenclature is through simple techniques. Organizations that have been collecting large customer data are increasingly seeing the need to use the data for swapping in and out and thrashing occurs ...
DevOps is often described as a combination of technology and culture. Without both, DevOps isn't complete. However, applying the culture to outdated technology is a recipe for disaster; as response times grow and connections between teams are delayed by technology, the culture will die. A Nutanix Enterprise Cloud has many benefits that provide the needed base for a true DevOps paradigm.
SYS-CON Events announced today that Interoute has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Interoute is the owner operator of Europe's largest network and a global cloud services platform, which encompasses over 70,000 km of lit fiber, 15 data centers, 17 virtual data centers and 33 colocation centers, with connections to 195 additional partner data centers. Our full-service Unifie...
SYS-CON Events announced today that Fusion, a leading provider of cloud services, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Fusion, a leading provider of integrated cloud solutions to small, medium and large businesses, is the industry’s single source for the cloud. Fusion’s advanced, proprietary cloud service platform enables the integration of leading edge solutions in the cloud, including cloud...
SYS-CON Events announced today that WineSOFT will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Based in Seoul and Irvine, WineSOFT is an innovative software house focusing on internet infrastructure solutions. The venture started as a bootstrap start-up in 2010 by focusing on making the internet faster and more powerful. WineSOFT’s knowledge is based on the expertise of TCP/IP, VPN, SSL, peer-to-peer, mob...