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Rewterz Threat Advisory – CVE-2021-34765 – Cisco Nexus Insights Authenticated Information Disclosure Vulnerability
September 2, 2021
Rewterz Threat Alert – SNAKE Ransomware – Active IOCs
September 2, 2021

Rewterz Threat Alert – ServHelper Backdoor – Active IOCs

September 2, 2021

Severity

High

Analysis Summary

ServHelper that is associated with the hacking group TA505 has been seen targeting financial and retail sectors. With the help of this backdoor, it enabled them to install and deploy other malware like Information Stealers (Predator Stealer), and Remote Access Trojans (RAT) (FlawedAmmy, NetSupport). It is delivered via NSIS installer, which, typically arrives as an attachment to a lure-based email. The loader checks to see if it is running in a virtualized environment to evade analysis techniques. It does this by checking for the presence of a Windows Defender file known to be present in virtualized environments. If this file is present, the installation will stop. If the file is not present, the installation proceeds. A PowerShell script contained within the NSIS installer’s directory is then executed. This script decrypts and invokes the main installer of ServHelper. Encryption is done with a combination of Base64 encoding and Triple DES Algorithm. This prevents commands from appearing in plain text. A further set of verification checks are done. The installer checks to ascertain if the instance has administrator privileges. If not, the installer will attempt to escalate privilege using DLL hacking with the assistance of Fubuki from UACME. This readily available collection of tools is typically used by penetration testers for research and privilege escalation. The installer also checks to see if the ROM size is greater than 2MB. If there is no ROM file, the installation stops as this is an indicator of virtualization. Once all components are decrypted, dropped, and installed, the ServHelper DLL is loaded. This specific variant only targets 64-bit Windows Operating Systems. Once the installation is complete, threat actors have backdoor access and are able to send and receive information.

Impact

  • File Encryption
  • Exposure of Sensitive Data
  • Information Theft
  • Cryptomining

Indicators of Compromise

MD5

  • 2849a8738acaf164bfb8b04d00c37804
  • f5c18800b50b8b1e04331c1ead5d8fb6

SHA-256

  • b070b592c1285c5467ebd82a391cbee30c3d2cf3f7a58edbe63157789f7a6661
  • cca4cc0c3b8d5f78cb8a7c5fe53d2ed0edbec35f03ca2f574f9b4fad688af757

SHA-1

  • bf756f2022235f97a7eeded1d8ab3504dd314b7e
  • 1b80b9db1af6ca7db2c9f5103ab1fa9c945c5bb1

Remediation

  • Block all the threat indicators in your respective controls.
  • Search for IOCs in your environment.
  • Services
    • Assess
      • Compromise Assessment
      • APT Assessment
      • Penetration Testing
      • Secure Architecture Design & Review
      • Red Team Assessment
      • Purple Team Assessment
      • Social Engineering
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    • Respond
      • Incident Response
      • Incident Analysis
  • Transform
    • SOC Consultancy
    •     SOC Maturity Assessment
    •     SOC Model Evaluation
    •     SOC Gap Analysis
    •     SIEM Gap Analysis
    •     SIEM Optimization
    •     SOC Content Pack
  • Train
    • Security Awareness and Training
    • Tabletop Exercise
    • Simulated Cyber Attack Exercises
  • Managed Security
    • Managed Security Monitoring
      • Remote SOC
      • Onsite SOC
      • Hybrid SOC
    • Managed Security Services
      • Managed Detection and Response
      • Managed Endpoint Detection and Response
      • Managed Threat Intelligence
      • Managed Threat Hunting
      • Managed Risk-Based SOAR
      • Managed Penetration Testing
  • Solutions
  • Resources
    • Blog
    • Threat Advisory
  • Company
    • About Us
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    • Contact
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