Systems and methods of detecting and responding to ransomware on a cloud-based file storage system by identifying a volume of changes in the files stored on the cloud-based file storage system

Patent metadata

Field	Value
Publication number	US-12284206-B2
Application number	US-202117537433-A
Country	US
Kind code	B2
Filing date	Nov 29, 2021
Priority date	Aug 10, 2016
Publication date	Apr 22, 2025
Grant date	Apr 22, 2025

Abstract

The technology disclosed relates to detecting a ransomware attack on a cloud-based file storage system. The detecting includes collecting metadata on files at they are manipulated, storing the collected metadata as historical metadata, detecting multiple artifacts of the ransomware attack resulting from ransomware manipulation of the files by (i) comparing at least one of the extension, the magic number and the size included in the historical metadata to at least one of the extension, the magic number and the size included in current metadata of the files to identify a volume of changes in the files, and (ii) detecting that the identified volume of changes exceeds a change volume to determine that the ransomware attack is in progress, and identifying a user/machine that manipulated the files and responding to the determination that the ransomware attack is in progress by restricting further manipulation of other files by the identified user/machine.

First claim

What is claimed is:

1. A method of detecting a ransomware attack impacting a cloud-based file storage service, the method comprising:
collecting metadata on files stored on the cloud-based file storage service, wherein:
the collecting the metadata comprises:
collecting a first portion of the metadata using an inspective agent of a proxy device through an application programming interface to the cloud-based file storage service; and
collecting a second portion of the metadata using a client agent installed locally on client devices that manipulate the files stored on the cloud-based file storage service,

the cloud-based file storage service supports manipulation by creating, editing, and sharing the files, and
the collected metadata includes at least one of an extension of a file name, a magic number, and a size;

storing the collected metadata as historical metadata in a historical metadata storage, wherein the historical metadata storage is separate from and not under control of the cloud-based file storage service;
detecting multiple artifacts of the ransomware attack resulting from ransomware manipulation of the files, the detecting including:
comparing at least one of the extension, the magic number and the size included in the historical metadata to at least one of the extension, the magic number and the size included in current metadata of the files to identify a volume of changes in the files, and
detecting that the identified volume of changes exceeds a predetermined change volume to determine that the ransomware attack is in progress;

identifying a user and/or client device of the client devices that manipulated the files exhibiting the multiple artifacts; and
responding to the determination that the ransomware attack is in progress, wherein the responding comprises:
restricting further manipulation of other files on the cloud-based file storage service by the identified user and/or client device.

2. The method of claim 1 , wherein;
the collecting the metadata further comprises collecting a third portion of the metadata using an active agent of the proxy device; and
the proxy device is positioned between the client devices and the cloud-based file storage service.

3. The method of claim 1 , wherein the responding further comprises:
notifying the user and/or client device that the ransomware attack was detected; and
providing a location of the ransomware attack to the user and/or client device.

4. The method of claim 1 , wherein the responding further comprises:
isolating the cloud-based file storage service, the isolating comprising:
disconnecting the identified user and/or client device from the cloud-based file storage service, and
disconnecting additional users who have access to the cloud-based file storage service; and

preventing the identified user and/or client device from accessing the cloud-based file storage service.

5. The method of claim 1 , wherein the responding further comprises at least one of performing a backup of the files and performing a backup of the cloud-based file storage service on which the files are stored.

6. The method of claim 1 , wherein the responding further comprises:
forcing the identified user and/or client device to perform a local scan for the ransomware attack; forcing a scan for the ransomware attack on any other cloud-based file storage service for which the identified user and/or client device has access;
forcing additional users who have access to the cloud-based file storage service to perform the local scan for the ransomware attack; and
forcing a scan for the ransomware attack on any other cloud-based file storage service for which the additional users have access.

7. The method of claim 1 , wherein:
the responding further comprises restoring a previous backup of the cloud-based file storage service; and
the restoring of the previous backup is automated or performed with user interaction.

8. The method of claim 1 , wherein the responding further comprises:
determining a creator of a file having caused the ransomware attack to be initiated on the identified user and/or client device based on the current metadata and the historical metadata; and
identifying and performing a specific response mechanism of multiple response mechanisms based on the determined creator.

9. A method of detecting a ransomware attack impacting a cloud-based file storage service, the method comprising:
collecting content properties from payloads of files stored on the cloud-based file storage service, wherein:
the collecting the content properties comprises:
collecting a first portion of the content properties using an inspective agent of a proxy device through an application programming interface to the cloud-based file storage service; and
collecting a second portion of the content properties using a client agent installed locally on client devices that manipulate the files stored on the cloud-based file storage service,

the cloud-based file storage service supports manipulation by creating, editing, and sharing the files, and
the collected content properties include at least one of a computed entropy or layered entropy, a locality-sensitive hashing (LSH), and an indication of an occurrence of a stub;

storing the collected content properties as historical content properties in a historical content properties storage, wherein the historical content properties storage is separate from and not under control of the cloud-based file storage service;
detecting multiple artifacts of the ransomware attack resulting from ransomware manipulation of the files, the detecting including:
comparing at least one of the computed entropy or layered entropy, the LSH, and the indication of the occurrence of the stub included in the historical content properties to respective at least one of the computed entropy or layered entropy, the LSH, and the indication of the occurrence of the stub included in current content properties of the files to identify a volume of changes in the files, and
detecting that the identified volume of changes exceeds a predetermined change volume to determine that the ransomware attack is in progress;

identifying a user and/or client device of the client devices that manipulated the files exhibiting the multiple artifacts; and
responding to the determination that the ransomware attack is in progress, the responding comprising:
restricting further manipulation of other files on the cloud-based file storage service by the identified user and/or client device.

10. The method of claim 9 , wherein:
the collecting the content properties further comprises collecting a third portion of the content properties using an active agent of the proxy device; and
the proxy device is positioned between the client devices and the cloud-based file storage service.

11. The method of claim 9 , wherein the identified volume of changes are identified by determining a hamming distance between the LSH for the current content properties and the LSH for the historical content properties.

12. The method of claim 9 , wherein the responding further comprises:
calculating an entropy of the payloads of the files;
comparing the entropy of the payloads of the files with entropies of known user-initiated encryption techniques to determine whether or not the identified user and/or client device has implemented a user-initiated encryption technique;
identifying each of the files for which the identified user and/or client device has implemented the user-initiated encryption technique;
determining that the ransomware attack is in process by analyzing the current content properties of the files and the hi

Assignees

• Netskope Inc

Inventors

• Hittel Sean
• Narayanaswamy Krishna
• Balupari Ravindra K
• Ithal Ravi

Classifications

• H04L63/1433

  Vulnerability analysis · CPC title

• G06F21/565

  by checking file integrity · CPC title

• G06F21/566

  Dynamic detection, i.e. detection performed at run-time, e.g. emulation, suspicious activities · CPC title

• G06F21/552 Primary

  involving long-term monitoring or reporting · CPC title

• G06F2221/2101

  Auditing as a secondary aspect · CPC title