What You Will Learn
Take your system-based forensic knowledge onto the wire. Incorporate network evidence into your investigations, provide better findings, and get the job done faster.
It is exceedingly rare to work any forensic investigation that doesn't have a network component. Endpoint forensics will always be a critical and foundational skill for this career but overlooking their network communications is akin to ignoring security camera footage of a crime as it was committed. Whether you handle an intrusion incident, data theft case, employee misuse scenario, or are engaged in proactive adversary discovery, the network often provides an unparalleled view of the incident. Its evidence can provide the proof necessary to show intent, uncover attackers that have been active for months or longer, or may even prove useful in definitively proving a crime actually occurred.
FOR572: ADVANCED NETWORK FORENSICS: THREAT HUNTING, ANALYSIS AND INCIDENT RESPONSE was designed to cover the most critical skills needed for the increased focus on network communications and artifacts in today's investigative work, including numerous use cases. Many investigative teams are incorporating proactive threat hunting to their skills, in which existing evidence is used with newly-acquired threat intelligence to uncover evidence of previously-unidentified incidents. Others focus on post-incident investigations and reporting. Still others engage with an adversary in real time, seeking to contain and eradicate the attacker from the victim's environment. In these situations and more, the artifacts left behind from attackers' communications can provide an invaluable view into their intent, capabilities, successes, and failures.
In FOR572, we focus on the knowledge necessary to examine and characterize communications that have occurred in the past or continue to occur. Even if the most skilled remote attacker compromised a system with an undetectable exploit, the system still has to communicate over the network. Without command-and-control and data extraction channels, the value of a compromised computer system drops to almost zero. Put another way: Bad guys are talking - we'll teach you to listen.
This course covers the tools, technology, and processes required to integrate network evidence sources into your investigations, with a focus on efficiency and effectiveness. You will leave this week with a well-stocked toolbox and the knowledge to use it on your first day back on the job. We will cover the full spectrum of network evidence, including high--evel NetFlow analysis, low-level pcap-based dissection, ancillary network log examination, and more. We cover how to leverage existing infrastructure devices that may contain months or years of valuable evidence as well as how to place new collection platforms while an incident is underway.
Whether you are a consultant responding to a client's site, a law enforcement professional assisting cybercrime victims and seeking prosecution of those responsible, an on-staff forensic practitioner, or a member of the growing ranks of threat hunters, this course offers hands-on experience with real-world scenarios that will help take your work to the next level. Previous SANS SEC curriculum students and other network defenders will benefit from the FOR572 perspective on security operations as they take on more incident response and investigative responsibilities. SANS DFIR alumni can take their existing operating system or device knowledge and apply it directly to the network-based attacks that occur daily. In FOR572, we solve the same caliber of real-world problems without the use of disk or memory images.
Most of FOR572's hands-on labs have been developed together with the latest version of FOR508, Advanced Incident Response, Threat Hunting, and Digital Forensics. In these shared scenarios, you'll quickly see a hybrid approach to forensic examination that includes both host and network artifacts is ideal. Although our primary focus is on the network side of that equation, we will point out areas where the host perspective could provide additional context, or where the network perspective gives deeper insight. Both former and future FOR508 students will appreciate the nexus between these extensive evidence sets.
The hands-on labs in this class cover a wide range of tools and platforms, including the venerable tcpdump and Wireshark for packet capture and analysis; NetworkMiner for artifact extraction; and open-source tools including nfdump, tcpxtract, tcpflow, and more. Newly added tools in the course include the free and open-source SOF-ELK platform - a VMware appliance pre-configured with a tailored configuration of the Elastic stack. This "big data" platform includes the Elasticsearch storage and search database, the Logstash ingest and parsing engine, and the Kibana graphical dashboard interface. Together with the custom SOF-ELK configuration files, the platform gives forensicators a ready-to-use platform for log and NetFlow analysis. For full-packet analysis and hunting at scale, the free and open-source Moloch platform is also covered and used in a hands-on lab. Through all of the in-class labs, shell scripting skills are highlighted as quick and easy ways to rip through hundreds of thousands of data records.
FOR572 is an advanced course - we hit the ground running on day one. Bring your entire bag of skills: forensic techniques and methodologies, full-stack networking knowledge (from the wire all the way up to user-facing services), Linux shell utilities, and everything in between. They will all benefit you throughout the course material as you FIGHT CRIME. UNRAVEL INCIDENTS...ONE BYTE (OR PACKET) AT A TIME.
Syllabus (36 CPEs)Download PDF
Focus: Although many fundamental network forensic concepts align with those of any other digital forensic investigation, the network presents many nuances that require special attention. Today you will learn how to apply what you already know about digital forensics and incident response to network-based evidence. You will also become acclimated to the basic tools of the trade.
Network data can be preserved, but only if directly captured or documented while in transit. Whether tactical or strategic, packet capture methods are quite straightforward. You will re-acquaint yourself with tcpdump and Wireshark, some of the most common tools used to capture and analyze network packets, respectively. However, since long-term full-packet capture is still uncommon in most environments, many artifacts that can tell us about what happened on the wire in the past come from devices that manage network functions. You will learn about what kinds of devices can provide valuable evidence and at what level of granularity. We will walk through collecting evidence from one of the most common sources of network evidence - a web proxy server - then you'll go hands-on to find and extract stolen data from the proxy.
The Linux SIFT Workstation virtual machine, which has been loaded with network forensic tools, will be your primary toolkit for the week.
- Lab Environment Preparation
- tcpdump and Wireshark Hands-On
- Carve Exfiltrated Data
- Web Proxy Server Examination
- Role of a web proxy
- Proxy solutions - commercial and open source
- Squid proxy server
- Automated analysis
- Cache extraction
- Foundational Network Forensics Tools: tcpdump and Wireshark
- tcpdump re-introduction
- pcap file format
- Berkeley Packet Filter (BPF)
- Data reduction
- Useful command-line parameters
- Wireshark re-introduction
- User interface
- Display filters
- Useful features for network forensic analysis
- Network Evidence Acquisition
- Three core types: full-packet capture, Logs, NetFlow
- Capture devices: switches, taps, Layer 7 sources, NetFlow
- Planning to capture: strategies; commercial and home-built platforms
- Network Architectural Challenges and Opportunities
- Challenges provided by a network environment
- Future trends that will affect network forensics
FOCUS: There are countless network protocols that may be in use in a production network environment. We will cover those that are most likely to benefit the forensicator in typical casework, as well as several that help demonstrate analysis methods useful when facing new, undocumented, or proprietary protocols. By learning the "typical" behaviors of these protocols, we can more readily identify anomalies that may suggest misuse of the protocol for nefarious purposes. These protocol artifacts and anomalies can be profiled through direct traffic analysis as well as through the log evidence created by systems that have control or visibility of that traffic. While this affords the investigator with vast opportunities to analyze the network traffic, efficient analysis of large quantities of source data generally requires tools and methods designed to scale.
Knowing how protocols appear in their normal use is critical if investigators are to identify anomalous behaviors. By looking at some of the more frequently-used and high-impact network communication protocols, we will specifically focus on the ways in which they can be easily misused by an adversary or a malware author.
While no one course could ever exhaustively cover the dizzying list of protocols used in a typical network environment, you will build the skills needed to learn whatever new protocols may come your way. The ability to "learn how to learn" is critical, as new protocols are developed every day. Advanced adversaries also develop their own protocols. As you will see later in this class, successfully understanding and counteracting an adversary's undocumented protocol is a similar process to learning those you will see in this section.
Log data is one of the unsung heroes in the realm of network forensics. While the near-perfect knowledge that comes with full-packet capture seems ideal, it suffers from several shortfalls. It is often unavailable, as many organizations have not yet deployed or cannot deploy comprehensive collection systems. When they are in use, network capture systems quickly amass a huge volume of data, which is often difficult to process effectively and must be maintained in a rolling buffer covering just a few days or weeks. The increasing use of encryption for most network traffic also provides a significant barrier to analysis when using full-packet capture, leaving logs from a terminal point of the communication as the artifact with the most potential impact.
In this section, you will learn various logging mechanisms available to both endpoint and network transport devices. You will also learn how to consolidate log data from multiple sources, providing a broad corpus of evidence in one location. As the volume of log data increases, so does the need to consider automated analytic tools. You'll use the SOF-ELK platform for post-incident log aggregation and analysis, bringing quick and decisive insight to a compromise investigation.
- HTTP Profiling
- DNS Profiling, Anomalies, and Scoping
- SOF-ELK Log Aggregation and Analysis
- Hypertext Transfer Protocol (HTTP) Part 1: Protocol
- Forensic value
- Request/response dissection
- Useful HTTP fields
- HTTP tracking cookies
- HTTP/2 artifacts
- Artifact extraction
- Hypertext Transfer Protocol (HTTP) Part 2: Logs
- Log formats
- Expanded mod_forensic logging
- Analysis methods
- Domain Name Service (DNS): Protocol and Logs
- Architecture and core functionality
- Fast flux and domain name generation algorithms (DGAs)
- Logging methods
- Amplification attacks
- Forensic Network Security Monitoring
- Network Security Monitoring (NSM) emergence from Intrusion Detection Systems (IDSes)
- Zeek NSM platform
- Proactive/live use case
- Post-incident DFIR use case
- Logs created and formats used
- JSON parsing with the "jq" utility
- Community-ID flow hash value
- Logging Protocol and Aggregation
- Dual role: server and protocol
- Source and collection platforms
- Event dissection
- rsyslog configuration
- Microsoft Eventing
- Deployment model and capabilities
- Windows Event Forwarding
- Analysis mode
- Log Data Collection, Aggregation, and Analysis
- Benefits of aggregation: scale, scope, independent validation, efficiency
- Known weaknesses and mitigations
- Evaluating a comprehensive log aggregation platform
- Elastic Stack and the SOF-ELK Platform
- Basics and pros/cons of the Elastic stack
- Log-centric dashboards
- Use as a data exploration platform
Focus: Network connection logging, commonly called NetFlow, may be the single most valuable source of evidence in network investigations. Many organizations have extensive archives of flow data due to its minimal storage requirements. Since NetFlow does not capture any content of the transmission, many legal issues with long-term retention are mitigated. Even without content, NetFlow provides an excellent means of guiding an investigation and characterizing an adversary's activities from pre-attack through operations. Whether for moving within a victim's environment or for data exfiltration, adversaries must move their quarry around through the use of various file access protocols. By knowing some of the more common file access and transfer protocols, a forensicator can quickly identify an attacker's theft actions.
Just as even a fuzzy photo can provide valuable leads in a traditional investigation, NetFlow data can provide a network forensicator with extremely high-value intelligence about network communications. The key to extracting that value is in knowing how to use NetFlow evidence to drive more detailed investigative activities.
NetFlow is also an ideal technology to use in baselining typical behavior of an environment, and therefore, deviations from that baseline that may suggest malicious actions. Threat hunting teams can also use NetFlow to identify prior connections consistent with newly-identified suspicious endpoints or traffic patterns.
In this section, you will learn the contents of typical NetFlow protocols, as well as common collection architectures and analysis methods. You'll also learn how to distill full-packet collections to NetFlow records for quick initial analysis before diving into more cumbersome pcap files.
You'll then examine the File Transfer Protocol, including how to reconstruct specific files from an FTP session. While FTP is commonly used for data exfiltration, it is also an opportunity to refine protocol analysis techniques, due to its multiple-stream nature.
Lastly, you'll explore a variety of the network protocols unique to a Microsoft Windows or Windows-compatible environment. Significant time will be spent exploring the SMB protocol, used for file transfers and countless other purposes in a Microsoft Windows domain structure. Attackers frequently use these protocols to "live off the land" within the victim's environment. By using existing and expected protocols, the adversary can hide in plain sight and avoid deploying malware that could tip off the investigators to their presence and actions.
- Visual NetFlow Analysis with SOF-ELK
- Tracking Lateral Movement with NetFlow
- SMB Session Analysis and Reconstruction
- NetFlow Collection and Analysis
- Origins and evolution
- NetFlow v5 and v9 protocols
- Architectural components
- NetFlow artifacts useful for examining encrypted traffic
- Open-Source Flow Tools
- Using open-source tool sets to examine NetFlow data
- nfcapd, nfpcapd, and nfdump
- SOF-ELK: NetFlow ingestion and dashboards
- File Transfer Protocol (FTP)
- History and current use
- Shortcomings in today's networks
- Capture and analysis
- File extraction
- Microsoft Protocols
- Architecture and capture positioning
- SMB v2, and v3
Focus: Commercial tools are an important part of a network forensicator's toolkit. We'll explore the various roles that commercial tools generally fill, as well as how they may best be integrated to an investigative workflow. With the runaway adoption of wireless networking, investigators must also be prepared to address the unique challenges this technology brings to the table. However, regardless of the protocol being examined or budget used to perform the analysis, having a means of exploring full-packet capture is a necessity, and having a toolkit to perform this at scale is critical.
Commercial tools hold clear advantages in some situations a forensicator may typically encounter. Most commonly, this centers on scalability. Many open-source tools are designed for tactical or small-scale use. Whether using them for large-scale deployments or for specific niche functionalities, these tools can immediately address many investigative needs.
Additionally, we will address the forensic aspects of wireless networking. We will cover similarities with and differences from traditional wired network examinations, as well as what interesting artifacts can be recovered from wireless protocol fields. Some inherent weaknesses of wireless deployments will also be covered, including how attackers can leverage those weaknesses during an attack, and how they can be detected.
Finally, we will look at methods that can improve at-scale hunting from full-packet captures, even without commercial tooling. We will look at the open-source Moloch platform and how it can be used in live and forensic workflows. You'll receive a ready-to-use Moloch virtual machine and load source data from an incident we previously investigated, seeking additional clarity from the previously captured full-packet data.
- Automated Extraction with NetworkMiner
- Using Command-Line Tools for Analysis
- Network Forensic Analysis Using Moloch
- Simple Mail Transfer Protocol (SMTP)
- Lifecycle of an email message
- Artifacts embedded along the delivery pathway
- Adaptations and extensions
- Object Extraction with NetworkMiner
- Value of commercial tools in a DFIR workflow
- Capabilities and user interface
- Use cases for object extraction
- Limitations and mitigations
- Wireless Network Forensics
- Translating analysis of wired networks to the wireless domain
- Capture methodologies: Hardware and Software
- Useful protocol fields
- Typical attack methodologies based on protection mechanisms
- Automated Tools and Libraries
- Common tools that can facilitate large-scale analysis and repeatable workflows
- Libraries that can be linked to custom tools and solutions
- Chaining tools together effectively
- Full-Packet Hunting with Moloch
- Moloch architecture and use cases
- Methods of ingesting packet data for DFIR workflows
- Session awareness, filtering, typical forensic use cases
- Raw packet searching with hunt jobs
- Enrichment of extracted metadata
- Custom decoding with CyberChef
Focus: Advancements in common technology have made it easier to be a bad guy and harder for us to track them. Strong encryption methods are readily available and custom protocols are easy to develop and employ. Despite this, there are still weaknesses even in the most advanced adversaries' methods. As we learn what the attackers have deliberately hidden from us, we must operate carefully to avoid tipping our hats regarding the investigative progress - or the attacker can quickly pivot, nullifying our progress.
Encryption is frequently cited as the most significant hurdle to effective network forensics - for good reason. When properly implemented, encryption can be a brick wall in between an investigator and critical answers. However, technical and implementation weaknesses can be used to our advantage. Even in the absence of these weaknesses, the right analytic approach to encrypted network traffic can still yield valuable information about the content. We will discuss the basics of encryption and how to approach it during an investigation. The section will also cover flow analysis to characterize encrypted conversations.
We will also discuss undocumented protocols and the misuse of existing protocols for nefarious purposes. Specifically, we will address how to derive intelligence value with limited or nonexistent knowledge of the carrier protocol.
Finally, we will look at how common missteps can provide the attacker with clear insight to the forensicator's progress. This often leads to the attacker changing their tactics, confounding the investigator and even erasing all the progress made to that point. We'll address best practices on conducting investigations and in a compromised environment and ways to share hard-earned intelligence that mitigate the risks involved.
- SSL/TLS Profiling
- Undocumented Protocol Features
- Mini-Comprehensive Investigation
- Encoding, Encryption, and SSL/TLS
- Encoding algorithms
- Encryption algorithms
- Profiling SSL/TLS connections with useful negotiation fields
- Analytic mitigation
- Perfect forward secrecy
- Meddler-in-the-Middle (MITM)
- Malicious uses and their artifacts
- Benevolent uses and associated limitations
- Common MITM tools
- Network Protocol Reverse Engineering
- Using known protocol fields to dissect unknown underlying protocols
- Pattern recognition for common encoding algorithms
- Addressing undocumented binary protocols
- What to do after breaking the protocol
- Investigation OPSEC and Threat Intel
- Operational Security
- Basic analysis can tip off attackers
- How to mitigate risk without compromising quality
- Plan to share smartly
- Protect intelligence to mitigate risks
Focus: This section will combine all of what you have learned prior to and during this week. In groups, you will examine network evidence from a real-world compromise by an advanced attacker. Each group will independently analyze data, form and develop hypotheses, and present findings. No evidence from endpoint systems is available - only the network and its infrastructure.
Students will test their understanding of network evidence and their ability to articulate and support hypotheses through presentations made to the instructor and class. The audience will include senior-level decision makers, so all presentations must include executive summaries as well as technical details. Time permitting, students should also include recommended steps that could help to prevent, detect, or mitigate a repeat compromise.
- Capstone Lab
- Network Forensic Case
- Analysis using only network-based evidence
- Determine the original source of an advanced attacker's compromise
- Identify the attacker's actions while in the victim's environment
- Confirm what data the attacker stole from the victim
- Present executive-level summaries of your findings at the end of the day-long lab
- Document and provide low-level technical backup for findings
- Establish and present a timeline of the attacker's activities
GIAC Network Forensic Analyst
The GIAC Network Forensic Analyst (GNFA) certification validates a practitioner’s ability to perform examinations employing network forensic artifact analysis. GNFA certification holders have demonstrated an understanding of the fundamentals of network forensics, normal and abnormal conditions for common network protocols, processes and tools used to examine device and system logs, and wireless communication and encrypted protocols.
Network architecture, network protocols, and network protocol reverse engineering
Encryption and encoding, NetFlow analysis and attack visualization, security event & incident logging
Network analysis tools and usage, wireless network analysis, & open source network security proxies
A properly configured system is required to fully participate in this course. These requirements are the mandatory minimums. If you do not carefully read and follow these instructions, you will likely leave the class unsatisfied because you will not be able to participate in hands-on exercises that are essential to this course. Therefore, we strongly urge you to arrive with a system meeting all the requirements specified for the course.
This is common sense, but we will say it anyway. Back up your system before class. Better yet, do not have any sensitive data stored on the system. SANS can't responsible for your system or data.
MANDATORY FOR572 SYSTEM HARDWARE REQUIREMENTS
- CPU: 64-bit Intel i5/i7 (4th generation+) - x64 bit 2.0+ GHz processor or more recent processor is mandatory for this class (Important - Please Read: a 64-bit system processor is mandatory)
- It is critical that your CPU and operating system support 64-bit so that our 64-bit guest virtual machine will run on your laptop. VMware provides a free tool for Windows that will detect whether or not your host supports 64-bit guest virtual machines. For further troubleshooting, this article also provides good instructions for Windows users to determine more about the CPU and OS capabilities. For Macs, please use this support page from Apple to determine 64-bit capability.
- BIOS settings must be set to enable virtualization technology, such as "Intel-VTx". Be absolutely certain you can access your BIOS if it is password protected, in case changes are necessary. Test it!
- 16 GB (Gigabytes) of RAM or higher is mandatory for this class (Important - Please Read: 16 GB of RAM or higher of RAM is mandatory and minimum.)
- USB 3.0 Type-A port is required. At least one open and working USB 3.0 Type-A port is required. (A Type-C to Type-A adapter may be necessary for newer laptops.) (Note: Some endpoint protection software prevents the use of USB devices - test your system with a USB drive before class to ensure you can load the course data.)
- 200 Gigabytes of Free Space on your System Hard Drive - Free Space on Hard Drive is critical to host the VMs and data sets we distribute
- Local Administrator Access is required. This is absolutely required. Don't let your IT team tell you otherwise. If your company will not permit this access for the duration of the course, then you should make arrangements to bring a different laptop.
- Wireless 802.11 Capability - there are no wired networks in the classroom.
MANDATORY FOR572 HOST CONFIGURATION AND SOFTWARE REQUIREMENTS
- Host Operating System: Latest version of Windows 10 or macOS 10.15.x
- On Windows hosts, VMware products cannot coexist with the Hyper-V hypervisor. Disable Hyper-V and ensure VMware can boot a virtual machine. Disabling Hyper-V, Device Guard, and Credential Guard can be accomplished using these instructions.
- Please note: It is necessary to fully update your host operating system prior to the class to ensure you have the right drivers and patches installed to utilize the latest USB 3.0 devices.
- Linux hosts cannot be supported in the classroom due to their numerous variations. Students that wish to use Linux hosts must be experienced users or administrators, and must also be able to access ExFAT partitions using the appropriate kernel and/or FUSE modules.
PLEASE INSTALL THE FOLLOWING SOFTWARE PRIOR TO CLASS
- Microsoft Office (any version) w/Excel or OpenOffice w/Calc installed on your host - Note you can download Office Trial Software online (free for 30 days)
- Download and install VMware Workstation Pro 15.5.X+, VMware Player 15.5.X+ or Fusion 11.5+ on your system prior to class beginning. If you do not own a licensed copy of VMware Workstation or Fusion, you can download a free 30-day trial copy from VMware. VMware will send you a time-limited serial number if you register for the trial at their website. Also note that VMware Player offers fewer features than VMware Workstation, and Workstation is recommended for a more seamless student experience.
- Download and install 7Zip (for Windows Hosts) or Keka (for macOS)
Your course media will now be delivered via download. The media files for class can be large, some in the 40 - 50 GB range. You need to allow plenty of time for the download to complete. Internet connections and speed vary greatly and are dependent on many different factors. Therefore, it is not possible to give an estimate of the length of time it will take to download your materials. Please start your course media downloads as you get the link. You will need your course media immediately on the first day of class. Waiting until the night before the class starts to begin your download has a high probability of failure.
SANS has begun providing printed materials in PDF form. Additionally, certain classes are using an electronic workbook in addition to the PDFs. The number of classes using eWorkbooks will grow quickly. In this new environment, we have found that a second monitor and/or a tablet device can be useful by keeping the class materials visible while the instructor is presenting or while you are working on lab exercises.
"When I first became interested in computer and network security in the mid-1990s, the idea of "attacking" another computer network was still science fiction. Today, commercial, governmental, military, and intelligence entities have robust, integrated information security processes. Within the forensic community, we have seen developments that show the agility we must have to remain effective in the face of dynamic adversaries. Endpoint forensic practices will remain the keystone of digital forensics for the foreseeable futur - this is where the events ultimately occur, after all.
"We created FOR572: Advanced Network Forensics: Threat Hunting, Analysis, and Incident Response to address the most transient domain of digital forensics. Many enterprises have grown to the scale that identifying which handful of endpoints to examine among thousands is a significant challenge. Additionally, the network has become its own medium for incident response and investigation. Our ability to use evidence from all kinds of network devices as well as from captured network data itself will be critical to our success in addressing threats today and tomorrow. From low-grade "script kiddie" attacks to long-term, strategic state-sponsored espionage activity, the network is one of the few common elements found throughout the life cycle of an incident. FOR572 will provide you with the tools and methods to conduct network investigations within environments of all sizes, using scenarios developed from real-world cases. You will finish the course with valuable knowledge that you will use the first day back on the job, and with the methodologies that will help address future generations of adversaries' capabilities." - Phil Hagen
"When I first started my career in computer security, the term "advanced persistent threat" was unknown, yet I had personally recovered terabytes of data obtained from both commercial and government networks. The biggest cybersecurity threat in the news was the latest worm that would propagate through unsuspecting systems and cause more of a nuisance than actual destruction. What was known as the Russian Business Network wasn't even around yet. Network security monitoring was still in its infancy, with very little formal documentation or best practices, most of which were geared towards system administrators. While the Internet has continued to expand, we have all become more interconnected and the threat against our networks continues to grow. We wrote FOR572 as the class we wish we had when we were entering the field of network forensics and investigations - a class that not only provides background when needed but is primarily tailored toward finding evil using multiple data sources and performing a full scope investigation. I am confident this course provides the most up-to-date training covering topics both old and new, based on real-life experiences and investigations." - Mat Oldham