Malware analysis Signed MSI files, Raccoon and Amadey are used for installing ServHelper RAT

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Aug 17, 2014
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News summary​

  • Group TA505 has been active for at least seven years, making wide-ranging connections with other threat actors involved in ransomware, stealing credit card numbers and exfiltrating data. One of the common tools in TA505's arsenal is ServHelper. In mid-June, Cisco Talos detected an increase in ServHelper's activity. We investigated the activity and discovered a set of intertwined malware families and TTPs.
  • We found that ServHelper is being installed onto the targeted systems using several different mechanisms, ranging from fake installers for popular software to using other malware families such as Raccoon and Amadey as the installation proxies.
  • This threat demonstrates several techniques of the MITRE ATT&CK framework, most notably Scripting - T1064, PowerShell - T1059.001, Process Injection - T1055, Non-Standard Port - T1571, Remote Access Software - T1219, Input Capture - T1056, Obfuscated Files or Information - T1027, Ingress Tool Transfer - T1105, and Registry Run Keys/Startup Folder - T1547.001.

WHAT'S NEW?​

Although ServHelper has existed since at least early 2019, we detected the use of other malware families to install it. The installation comes as a GoLang dropper, .NET dropper or PowerShell script. Its activity is generally linked to Group TA505, but we cannot be certain that they are the exclusive users of this RAT.

ServHelper will also sometimes install a module that includes either Monero or Ethereum cryptocurrency mining tools.

HOW DID IT WORK?​

One path for infection starts with the compromise of a legitimate site that hosts cryptographically signed MSI installers. These install popular software such as Discord. However, they also launch a variant of the Raccoon stealer, which downloads and installs a ServHelper RAT if instructed by the command and control (C2) server.

Attackers also deploy the ServHelper RAT with a variant of the Amadey malware which gets a full command line from the server to install an initial PowerShell downloader component for ServHelper.

ServHelper includes the functionality to remotely control the infected system, log keystrokes, exfiltrate users' confidential data, launch RDP sessions, install cryptomining software and install the NetSupport remote access tool.

SO WHAT?​

Although many threat actors, such as TA505 or its associated groups — to which we attribute these campaigns with moderate confidence — have been affected by the arrests of several CLOP members in Ukraine, they continued to operate using a different set of tools. These attacks are geared toward taking control over the infected systems and stealing confidential data which the group will likely leverage for financial gain later on.

Users need to make sure they install software only from trusted sources. Even if installers are signed with a valid certificate, that does not mean that the functionality is legitimate.

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