Exfiltration via USB Mass Storage Device

A Data Classification Policy establishes a standard for handling data by setting out criteria for how data should be classified and subsequently managed and secured. A classification can be applied to data in such a way that the classification is recorded in the body of the data (such as a footer in a text document) and/or within the metadata of a file.

An Acceptable Use Policy (AUP) is a set of rules outlining acceptable and unacceptable uses of an organization's computer systems and network resources. It acts as a deterrent to prevent employees from conducting illegitimate activities by clearly defining expectations, reinforcing legal and ethical standards, establishing accountability, specifying consequences for violations, and promoting education and awareness about security risks.

Using Group Policy on Windows it is possible to block execute, read, and write operations related to a removeable disk, such as an SD card or USB mass storage devices.

In the Group Policy Editor, navigate to:
Computer Configuration -> Administrative Templates -> System -> Removable Storage Access

Open the following policies and set them all to Enabled:

Removeable Disk: Deny execute access

Removeable Disk: Deny read access

Removeable Disk: Deny write access

An agent capable of Endpoint Detection and Response (EDR) is a software agent installed on organization endpoints (such as laptops and servers) that (at a minimum) records the Operating System, application, and network activity on an endpoint.

Typically EDR operates in an agent/server model, where agents automatically send logs to a server, where the server correlates those logs based on a rule set. This rule set is then used to surface potential security-related events, that can then be analyzed.

An EDR agent typically also has some form of remote shell capability, where a user of the EDR platform can gain a remote shell session on a target endpoint, for incident response purposes. An EDR agent will typically have the ability to remotely isolate an endpoint, where all network activity is blocked on the target endpoint (other than the network activity required for the EDR platform to operate).

An agent capable of User Activity Monitoring (UAM) is a software agent installed on organization endpoints (such as laptops); typically, User Activity Monitoring agents are only deployed on endpoints where a human user Is expected to conduct the activity.

The User Activity Monitoring agent will typically record Operating System, application, and network activity occurring on an endpoint, with a focus on activity that is or can be conducted by a human user. The purpose of this monitoring is to identify undesirable and/or malicious activity being conducted by a human user (in this context, an Insider Threat).

Typical User Activity Monitoring platforms operate in an agent/server model where activity logs are sent to a server for automatic correlation against a rule set. This rule set is used to surface activity that may represent Insider Threat related activity such as capturing screenshots, copying data, compressing files or installing risky software.

Other platforms providing related functionality are frequently referred to as User Behaviour Analytics (UBA) platforms.

An agent capable of User Behaviour Analytics (UBA) is a software agent installed on organizational endpoints (such as laptops). Typically, User Activity Monitoring agents are only deployed on endpoints where a human user is expected to conduct the activity.

The User Behaviour Analytics agent will typically record Operating System, application, and network activity occurring on an endpoint, focusing on activity that is or can be conducted by a human user. Typically, User Behaviour Analytics platforms operate in an agent/server model where activity logs are sent to a server for automatic analysis. In the case of User Behaviour Analytics, this analysis will typically be conducted against a baseline that has previously been established.

A User Behaviour Analytic platform will typically conduct a period of ‘baselining’ when the platform is first installed. This baselining period establishes the normal behavior parameters for an organization’s users, which are used to train a Machine Learning (ML) model. This ML model can then be later used to automatically identify activity that is predicted to be an anomaly, which is hoped to surface user behavior that is undesirable, risky, or malicious.

Other platforms providing related functionality are frequently referred to as User Activity Monitoring (UAM) platforms.

Located at HKLM\SYSTEM\MountedDevices, this registry key provides insights into the most recently mounted devices mounted to the system, such as USB drives, hard drives, and other storage devices. It records detailed information that may include; drive letter, volume GUID, and information from the USBSTOR registry key.

These details can be cross-referenced with evidence in the USB and USBSTOR registry keys.

Shellbags are a set of Windows registry keys that contain details about a user-viewed folder, such as its size, position, thumbnail, and timestamps. Typically Shellbag information is created for folders that have been opened and closed with Windows File Explorer and default settings adjusted. However, Shellbag information can be created under various situations across different versions of Windows.

Shellbags are located in the following registry keys:

Windows XP

NTUSER.DAT\Software\Microsoft\Windows\Shell\BagMRU
NTUSER.DAT\Software\Microsoft\Windows\Shell\Bags
NTUSER.DAT\Software\Microsoft\Windows\ShellNoRoam\BagMRU
NTUSER.DAT\Software\Microsoft\Windows\ShellNoRoam\Bags

Windows 7 and later

NTUSER.DAT\Software\Microsoft\Windows\Shell\BagMRU
NTUSER.DAT\Software\Microsoft\Windows\Shell\Bags
UsrClass.dat\Local Settings\Software\Microsoft\Windows\Shell\BagMRU
UsrClass.dat\Local Settings\Software\Microsoft\Windows\Shell\Bags
 

Shellbags can disclose information about USB removable storage drives that are connected to the system, disclosing the drive letter and any files that were accessed from the drive.

MountPoints2 is a Windows Registry key used to store information about previously connected removable devices, such as USB drives, CDs, and other external storage media. It is located at:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2

Each subkey under MountPoints2 represents a unique device, often identified by its GUID (Globally Unique Identifier) or other unique identifier.
These subkeys can contain various values that describe the properties and behavior of the corresponding device, such as the assigned drive letter, volume label, and other relevant data.

Located at HKLM\SYSTEM\ControlSet001\Enum\USB, it provides a rich information source about USB devices connected to a Windows system. The information you can typically find under this key includes; connection status, information from the USBSTOR registry key, last write time, and installation date.

These details can be cross-referenced with evidence in the MountedDevices and USBSTOR registry keys.

Located at HKLM\SYSTEM\ControlSet001\Enum\USBSTOR in the Windows registry, it holds comprehensive details for each device connected via USB ports. This key features individual subkeys for every device connected to the system, where you can find extensive information, including; timestamps, serial number, unique ID, container ID, friendly name, device name, make, model and type.

These details can be cross-referenced with evidence in the MountedDevices and USB registry keys.

This Event log is not enabled by default.

The log file can be located at %systemroot%\System32\winevt\Logs\Microsoft-Windows-DriverFrameworks-UserMode%4Operational.evtx.

Once a USB drive is connected, the logs will begin to populate. Each log entry includes the device ID (as registered in the system), the time it was logged, and a description of the occurrence.

Event ID 2003 marks the initiation of a USB device connection. This event logs when a USB device is first recognized and connected to the system. Event IDs 2100 and 2102 track when a USB device is disconnected or a connection session ends. Event ID 2100 typically captures an intermediate disconnection, while Event ID 2102 logs the final disconnection of the USB device. By correlating the timestamps associated with the same Device ID, an investigator can determine the duration for which a USB device was connected to the system.

The setupapi.dev file, located in %systemroot%\INF\setupAPI.dev, is a text file that documents the details of the first time a specific device was connected to the computer. This file ensures the system has the appropriate drivers to read and access the media. Each log entry in this file begins with a section header, where the latter part includes the device ID. This file does not provide information as to when the device was unplugged or disconnected.