MA: How Malware Analysis Works

Document created by RSA Information Design and Development on Sep 15, 2017Last modified by RSA Information Design and Development on Sep 19, 2017
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NetWitness Suite Malware Analysis is an automated malware analysis processor designed to analyze certain types of file objects (for example, Windows PE, PDF, and MS Office) to assess the likelihood that a file is malicious. Using Malware Analysis, the malware analyst can prioritize the massive number of files captured in order to focus analysis efforts on the files that are most likely to be malicious. 

Malware Analysis detects indicators of compromise using four distinct analysis methodologies:

  • Network Session Analysis (network)
  • Static File Analysis (static)
  • Dynamic File Analysis (sandbox)
  • Security Community Analysis (community)

Each of the four distinct analysis methodologies is designed to compensate for inherent weaknesses in the others. For example, Dynamic File Analysis can compensate for Zero-Day attacks that are not detected during the Security Community Analysis phase. By avoiding malware analysis that strictly focuses on one methodology, the analyst is more likely to be shielded from false negative results.

In addition to the built-in indicators of compromise, beginning with NetWitness Suite 10.3, Malware Analysis also supports indicators of compromise written in YARA. YARA is a rule language, which allows malware researchers to identify and classify malware samples. This allows IOC authors to add detection capabilities to RSA Malware Analysis by authoring YARA rules and publishing them in RSA Live. These YARA-based IOCs in RSA Live will automatically be downloaded and activated on the subscribed host, to supplement the existing analysis that is performed in each analyzed file. 

Beginning with NetWitness Suite 10.4, Malware Analysis has features that support alerts for Incident Management.

Functional Description

This figure depicts the functional relationship between the Core services (the Decoder, Concentrator, and Broker), the Malware Analysis service, and the NetWitness Server.

Relationship between core services, Malware Analysis service, and the Netwitness server

The Malware Analysis service analyzes file objects using any combination of the following methods:

  • Continuous automatic polling of a Concentrator or Broker to extract sessions identified by a parser as potentially carrying malware content.
  • On-demand polling of a Concentrator or Broker to extract sessions identified by a malware analyst as potentially carrying malware content.
  • On-demand upload of files from a user-specified folder.

When automatic polling of a Concentrator or Broker is enabled, the Malware Analysis service continuously extracts and prioritizes executable content, PDF documents, and Microsoft Office documents on your network, directly from data captured and analyzed by your Core service. Because the Malware Analysis service connects to a Concentrator or Broker to extract only those executable files that are flagged as possible malware, the process is both rapid and efficient. This process is continuous and does not require monitoring.

When on-demand polling of a Concentrator or Broker is chosen, the malware analyst uses Investigation to drill into captured data and choose sessions to be analyzed. The Malware Analysis service uses this information to automatically poll the Concentrator or Broker and to download the specified sessions for analysis.

On-demand upload of files provides a method for the analyst to review files captured external to the Core infrastructure. The malware chooses a folder location and identify one or more files to be uploaded and analyzed by Malware Analysis. These files are analyzed using the same methodology as files automatically extracted from network sessions. 

Analysis Method

For the Network analysis, the Malware Analysis service looks for characteristics that seem to deviate from the norm, much as an analyst does. By looking at hundreds to thousands of characteristics and combining the results into a weighted scoring system, legitimate sessions that coincidentally have a few abnormal traits are dismissed, while the actual bad ones are highlighted. A user can learn patterns that indicate anomalous activity in the sessions as indicators that warrant further investigation, Indicators of Compromise.

The Malware Analysis service can perform Static analysis against suspicious objects it finds on the network and determine whether those objects contain malicious code. For Community analysis, new malware detected on the network is pushed to the RSA Cloud for checking against RSA's own malware analysis data and feeds from the SANS Internet Storm Center, SRI International, the Department of the Treasury and VeriSign. For Sandbox analysis, the services can also push data into major security, information and event management (SIEM) hosts (the ThreatGrid Cloud). 

Malware Analysis has a unique method for analysis that is partnered with industry leaders and experts, so their technologies can enrich the Malware Analysis scoring system.

NetWitness Server Access to the Malware Analysis Service

The NetWitness Server is configured to connect to the Malware Analysis service and import tagged data for deeper analysis in Investigation. Access is based on three subscription levels.

  • Free subscription: All NetWitness Suite customers have a free subscription, with a free trial key for ThreatGrid analysis. The Malware Analysis service is rate-limited to 100 file samples per day. The number of samples (within the set of files from above) submitted to the ThreatGrid Cloud for sandbox analysis is limited to 5 per day. If one network session had 100 files in it, customers would hit the rate limit after processing the one network session. If 100 files were manually uploaded, that would cause the rate limit to be reached.
  • Standard subscription tier: The number of submissions to the Malware Analysis service is unlimited. The number of samples submitted to the ThreatGrid Cloud for sandbox analysis is 1000 per day.
  • Enterprise subscription tier: The number of submissions to the Malware Analysis service is unlimited. The number of samples submitted to the ThreatGrid Cloud for sandbox analysis is 5000 per day.

Scoring Method

By default, the Indicators of Compromise (IOC) are tuned to reflect industry best practices. Each IOC is assigned a score ranging from -100 (good) to +100 (bad). During analysis, the IOCs that trigger cause the score to move upward or downward to indicate the likelihood that the sample is malicious. The tuning of IOCs is exposed in NetWitness Suite so that the malware analyst can choose to override the assigned score or to disable an IOC from being evaluated. The analyst has the flexibility to either use the default tuning, or to completely customize the tuning to specific needs.

YARA-based IOCs are interleaved with the built-in IOCs within each built-in category and are not distinguished from native IOCs. When viewing IOCs in the Service Configuration view, administrators can select YARA from the Module selection list to see a list of YARA rules. 

After a session is imported into NetWitness Suite, all of the viewing and analysis capabilities in Investigation are available to further analyze Indicators of Compromise. When viewed in Investigation, YARA IOCs are distinguished from the built-in native IOCs by the tag Yara rule.

Deployment

The Malware Analysis service is with a dedicated RSA Malware Analysis host.The dedicated Malware Analysis host has an onboard Broker which connects to the Core infrastructure (either another Broker or a Concentrator). Prior to this connection, a collection of parsers and feeds must be added to the Decoders that are connected to the Concentrators and Brokers from which the Malware Analysis service pulls data.  This allows suspicious data files to be marked for extraction. These files are malware analysis tagged content available through the RSA Live content management system.

Scoring Modules

RSA NetWitness Suite Malware Analysis analyzes and scores sessions and the embedded files within these sessions by scoring four categories: Network, Static Analysis, Community, and Sandbox. Each category comprises many individual rules and checks that are used to calculate a score between 1-100. The higher the score, the more likely the session is to be malicious and worthy of more in-depth follow-on investigation.

Malware Analysis can facilitate a historical investigation into events leading up to a network alarm or incident. If you know that a certain type of activity is taking place on your network, you can select only the reports of interest to examine the content of data collections. You can also modify behavior for each scoring category based on the scoring category or the file type (Windows PE, PDF, and Microsoft Office).

Once you become familiar with data navigation methods, you can explore the data more completely through:

  • Searching for specific types of information
  • Reviewing specific content in detail.

Category scores for Network, Static Analysis, Community, and Sandbox are maintained and reported independently. When events are viewed based on the independent scores, as long as one category detects malware, it is evident in the Analysis section.

Network

The first category examines each core network session to determine if the delivery of the malware candidates was suspicious. For example, benign software being downloaded from a well-known safe site, using proper ports and protocols, is considered less suspicious than downloading software known to be malicious from a known dubious download site. Sample factors used in the scoring of this criteria set may include sessions that:

  • Contain threat feed information
  • Connect to well-known bad sites
  • Connect to high-risk domains/countries (for example, .cc domain)
  • Use well-known protocols on non-standard ports
  • Contain obfuscated JavaScript

Static Analysis

The second category analyzes each file in the session for signs of obfuscation in order to predict the likelihood of the file behaving maliciously if allowed to run. For example, software that links to networking libraries is more likely to perform suspicious network activity. Sample factors used in the scoring of this criteria set may include:

  • Files found to be XOR encoded
  • Files found embedded within non-EXE formats (for example, PE file found embedded in a GIF format)
  • Files linking to higher risk import libraries
  • Files highly deviating from the PE Format

Community

The third category scores the session and files based on the collective knowledge of the security community. For example, files whose fingerprint/hash is already known to be good or bad by respected anti-virus (AV) vendors is scored accordingly. Files are also scored based on knowledge that a file was delivered from a site known to be good or bad by the security community.

Community scoring also indicates whether the AV on your network flagged the files as malicious. It does not indicate that the resident AV product acted to protect your system.

Sandbox

The fourth category examines the behavior of the software by actually running it in a sandbox environment. By running the software to watch its behavior, a score can be calculated by identifying well-known malicious activity. For example, software that configures itself to autostart on each reboot and make IRC connections would score higher than a file with no known bad behavior.

Roles and Permissions for Analysts

This topic identifies the user roles and permissions required for a user to conduct malware analysis in NetWitness Suite. If you cannot perform an analysis task or see a view, the administrator may need to adjust the roles and permissions configured for you.

Required Roles and Permissions

RSA NetWitness Suite manages security by providing access to views and functions using both system permissions and permissions on individual services.

On the system level, the user needs to be assigned a system role, in the Administration > System view, that provides access to specific views and functions.

The default Malware_Analysts role in NetWitness Suite 11.0 is assigned all of the permissions listed below. If necessary, an Administrator can create a custom role with some combination of the following permissions:

  • Access Investigation Module (required)
  • Investigation - Navigate Events
  • Investigation - Navigate Values
  • Access Incident Module
  • View and Manage Incidents
  • View Malware Events (to view events)
  • File Download (to download files from the Malware Analysis service)
  • Initiate Malware Scan (to initiate a one-time service scan or one-time file upload)
  • Dashlet permissions for convenience: Dashlet - Investigate Top Values Dashlet, Dashlet - Investigate Service List Dashlet, Dashlet - Investigate Jobs Dashlet, Dashlet - Investage Shortcuts Dashlet.

A use case for creating a custom role would be a Junior Malware Analyst role, with limited permissions that do not include the File Download permission.

On specific services, a malware analyst needs to be a member of the Analysts group, or to a group that has the two default permissions assigned to the Analyst group: sdk.meta and sdk.content. Users who have these permissions can use specific applications, run queries, and view content for purpose of analysis on the service.

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