Join us at Netskope’s SASE Summit, coming to a city near you! Register now.

  • Security Service Edge Products

    Protect against advanced and cloud-enabled threats and safeguard data across all vectors.

  • Borderless SD-WAN

    Confidently provide secure, high-performance access to every remote user, device, site, and cloud.

  • Platform

    Unrivaled visibility and real-time data and threat protection on the world's largest security private cloud.

The platform of the future is Netskope

Intelligent Security Service Edge (SSE), Cloud Access Security Broker (CASB), Cloud Firewall, Next Generation Secure Web Gateway (SWG), and Private Access for ZTNA built natively into a single solution to help every business on its journey to Secure Access Service Edge (SASE) architecture.

Go to Products Overview
Netskope video
Borderless SD-WAN: Ushering in the New Era of Borderless Enterprise

Netskope Borderless SD-WAN offers an architecture that converges zero trust principles and assured application performance to provide unprecedented secure, high-performance connectivity for every site, cloud, remote user, and IoT device.

Read the article
Borderless SD-WAN
Netskope delivers a modern cloud security stack, with unified capabilities for data and threat protection, plus secure private access.

Explore our platform
Birds eye view metropolitan city
Make the move to market-leading cloud security services with minimal latency and high reliability.

Learn about NewEdge
Lighted highway through mountainside switchbacks
Safely enable the use of generative AI applications with application access control, real-time user coaching, and best-in-class data protection.

Learn how we secure generative AI use
Safely Enable ChatGPT and Generative AI
Zero trust solutions for SSE and SASE deployments

Learn about Zero Trust
Boat driving through open sea
Netskope enables a safe, cloud-smart, and fast journey to adopt cloud services, apps, and public cloud infrastructure.

Learn about Industry Solutions
Wind turbines along cliffside
  • Our Customers

    Netskope serves more than 2,000 customers worldwide including more than 25 of the Fortune 100

  • Customer Solutions

    We are here for you and with you every step of the way, ensuring your success with Netskope.

  • Training and Certification

    Netskope training will help you become a cloud security expert.

We help our customers to be Ready for Anything

See our Customers
Woman smiling with glasses looking out window
Netskope’s talented and experienced Professional Services team provides a prescriptive approach to your successful implementation.

Learn about Professional Services
Netskope Professional Services
Secure your digital transformation journey and make the most of your cloud, web, and private applications with Netskope training.

Learn about Training and Certifications
Group of young professionals working
  • Resources

    Learn more about how Netskope can help you secure your journey to the cloud.

  • Blog

    Learn how Netskope enables security and networking transformation through security service edge (SSE).

  • Events & Workshops

    Stay ahead of the latest security trends and connect with your peers.

  • Security Defined

    Everything you need to know in our cybersecurity encyclopedia.

Security Visionaries Podcast

Bonus Episode 2: The Magic Quadrant for SSE and Getting SASE Right
Mike and Steve discuss the Gartner® Magic Quadrant™ for Security Service Edge (SSE), Netskope’s positioning, and how the current economic climate will impact the SASE journey.

Play the podcast
Bonus Episode 2: The Magic Quadrant for SSE and Getting SASE Right
Latest Blogs

How Netskope can enable the Zero Trust and SASE journey through security service edge (SSE) capabilities.

Read the blog
Sunrise and cloudy sky
Netskope AWS Immersion Day World Tour 2023

Netskope has developed a variety of hands-on labs, workshops, in-depth webinars and demos to educate and assist AWS customers in the usage and deployment of Netskope products.

Learn about AWS Immersion Day
AWS Partner
What is Security Service Edge?

Explore the security side of SASE, the future of network and protection in the cloud.

Learn about Security Service Edge
Four-way roundabout
  • Company

    We help you stay ahead of cloud, data, and network security challenges.

  • Why Netskope

    Cloud transformation and work from anywhere have changed how security needs to work.

  • Leadership

    Our leadership team is fiercely committed to doing everything it takes to make our customers successful.

  • Partners

    We partner with security leaders to help you secure your journey to the cloud.

Supporting sustainability through data security

Netskope is proud to participate in Vision 2045: an initiative aimed to raise awareness on private industry’s role in sustainability.

Find out more
Supporting Sustainability Through Data Security
Highest in Execution. Furthest in Vision.

Netskope recognized as a Leader in the 2023 Gartner® Magic Quadrant™ for Security Service Edge.

Get the report
Netskope recognized as a Leader in the 2023 Gartner® Magic Quadrant™ for Security Service Edge.
Thinkers, builders, dreamers, innovators. Together, we deliver cutting-edge cloud security solutions to help our customers protect their data and people.

Meet our team
Group of hikers scaling a snowy mountain
Netskope’s partner-centric go-to-market strategy enables our partners to maximize their growth and profitability while transforming enterprise security.

Learn about Netskope Partners
Group of diverse young professionals smiling

cuteRansomware Uses Google Docs to Fly Under Radar

Jul 12 2016
Tags
Cloud Best Practices
Cloud Malware
Cloud Security
Netskope Threat Research Labs
Ransomware
Tools and Tips
Vulnerability Advisory

Ransomware is gaining in popularity. It is a real threat as it seeks to find and encrypt users’ important files and then hold those files for ransom. Netskope has detected and reported on an increase in cloud apps as a delivery mechanism for ransomware, particularly in obfuscated JavaScript as well as Microsoft Word documents using macros functions.

Here we are calling your attention to a ransomware module called cuteRansomware. What makes cuteRansomware important is its use of cloud service, Google Docs, in order to transmit encryption keys and collect user information without detection. This highlights the importance of detecting malware in cloud apps, and not just in the sanctioned ones, but the unsanctioned ones as well. It also highlights the importance of anticipating such an attack by identifying where your sensitive content is in the cloud and ensuring that you have backups of those important files.

A few months ago, our research team noticed that a user with a GitHub account “aaaddress1” published source code for a ransomware module based on C# called “my-Little-Ransomware.” Since the code was publicly available, others began using it. Indeed, a security researcher at AVG spotted a malicious modified Chinese version of my-Little-Ransomware. The ransomware is also dubbed “cuteRansomware” because of the mutex name used by the original author, so in this blog we will refer it as such. Although the ransomware sample was mostly cut-and-paste from the original, the use of Google Docs to send RSA keys over the network drew our attention. Analyzing further, below is the AES code implementation in this cuteRansomware sample, which looks very similar to the my-Little-Ransomware code.cuteransomware_1Figure 1: AES implementation code used in cuteRansomware sample

Here is another modification by the authors in the “encryptFile()” routine, which also drives the point that the malicious actors behind this ransomware seem to be creating their own ransomware binary by modifying some of the information provided in the original my-Little-Ransomware.

cuteransomware_2Figure 2: EncryptFile routine code targeting only specific file extensions

The cuteRansomware sample sought only to encrypt a small handful of extensions compared to the original list, including .bmp, .png, .jpg, .zip, .txt, .pdf, .pptx, .docx, .py, .cpp, .pcap, .enc, .pem, and .csr. The extension name of the encrypted files was also changed to “.encrypted” in Chinese. Comparison of the my-Little-Ransomware and cuteRansomware code samples shows many similarities, including the the side-by-side comparison below.

cuteransomware_3Figure 3: Source code comparison between original and malicious sample.

The most interesting aspect of cuteRansomware was in the main() function of the binary itself in which it instructs that information collected from the victim’s machine be sent to a Google Doc.

cuteransomware_4Figure 4: Main routine using Google Doc URL for sending keys

The screenshot from above with the translation from Chinese to English shows further message details.

cuteransomware_5Figure 5: Translation of Chinese strings into English

Analyzing the code, the ransomware simply creates a mutex with name “cuteRansomware,” encrypts random files, and writes a couple of text files under %TEMP% directory. Although it does not lock the user’s computer screen, it delivers a pop-up from a text file with a small message in Chinese stating that the user’s files have been encrypted. Then comes the interesting part: The binary captures the computer name of the victim and uploads it and the RSA key for encrypting/decrypting files to the malicious actor-controlled Google Docs form. At the time of writing this blog, the form was still available on the Google Docs (we have notified Google’s security team about this). The network traffic depicted below shows communication with Google Docs over SSL/TLS protocol.

cuteransomware_6Figure 6: Network traffic of data being sent to Google Docs via SSL/TLS

By setting up a fiddler proxy, we can get a deeper look into the data being sent to the Google Docs form created by the malicious actor.

cuteransomware_7Figure 7: Decrypted SSL traffic shows data sent over the network cuteransomware_8Figure 8: Actual homepage of Google Doc URL

As we know, Google Docs uses HTTPS by default and the network data transmission over SSL can easily bypass traditional security solutions such as a firewall, intrusion prevention system, or next generation firewall. We believe this is critical. As malicious actors make increasing use of the cloud for both delivering malware and exfiltrating data via command-and-control, traditional detection tools’ lack of visibility into SSL becomes a huge benefit to them. Additionally, the inability of traditional tools to look into SSL traffic of unsanctioned apps becomes important.

Moreover, the use of a popular cloud app like Google Docs presents another challenge. For organizations using Google Docs as a productivity tool, it’s virtually impossible to block it outright. To prevent this ransomware from using Google Docs, you need to be able to selectively block the specific app instance associated with this ransomware while allowing your sanctioned instance of Google Docs to continue working.

Undoubtedly, we are seeing a sharp increase in ransomware attacks in recent months. Although this seems to be a basic ransomware created by modifying the my-Little-Ransomware source code, the use of cloud services like Google Docs may be a signal about attacker intentions to use cloud services in the future. Also, we may even conclude that ransomware authors will abuse cloud services not only for storing keys but also for their command-and-control (C&C) communications.

Note about Netskope’s detection/remediation for cuteRansomware

Netskope customers using Netskope Active Threat Protection are protected from cuteRansomware. Customers will notice cuteRansomware is detected generically as Trojan.Generc.17258518. Customers deploying Cloud Malware and Threat Protection in Active mode will notice detections of the Command and Control activity as illustrated in the the following details in the SkopeIT events which is related to cuteRansomware communication with Google Docs.

cuteransomware-9

In order to anticipate and protect against this and other ransomware delivered via cloud apps, we recommend IT and users do the following:

  • Detect and remediate all malware in sanctioned cloud apps
  • Detect and remediate all malware being downloaded from unsanctioned cloud apps
  • Actively track usage of unsanctioned instances of trusted cloud apps and enforce DLP policies to control files and data entering and leaving your corporate environment
  • Regularly back up and turn on versioning for critical content in cloud apps
  • Disable macros in all Microsoft Office programs
  • Administrators should block macros by default via a group policy
  • Warn users to avoid opening untrusted attachments regardless of their extension or filename
  • Keep systems and antivirus updated with the latest releases and patches