Analysis by: Augusto II Remillano
ALIASES:

Trojan:Win32/Skeeyah.A!rfn (Microsoft); W32/Kryptik.GHUN!tr (Fortinet)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It gathers certain information on the affected computer.

It connects to certain websites to send and receive information. It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 216,064 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 27 Jun 2018
Payload: Connects to URLs/IPs, Collects system information

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Trojan drops the following copies of itself into the affected system:

  • %Application Data%\Microsoft\Windows\{Random1}\{Random2}.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It drops the following files:

  • %System%\Tasks\Opera scheduled Autoupdate 4086469641

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It creates the following folders:

  • %Application Data%\Microsoft\Windows\{Random1}

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • hashed computer name and volume serial number

It injects codes into the following process(es):

  • svchost.exe
  • explorer.exe

Autostart Technique

This Trojan drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\{Random1}.lnk

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

The scheduled task executes the malware every:

  • 10 minutes

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tasks\{GUID value}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tree\Opera scheduled Autoupdate 4086469641

It also creates the following registry entry(ies) as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tasks\{GUID value}
Path = \Opera scheduled Autoupdate 4086469641

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tasks\{GUID value}
Hash = {Hex value}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tasks\{GUID value}
Triggers = {Hex value}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tasks\{GUID value}
DynamicInfo = {Hex value}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tree\Opera scheduled Autoupdate 4086469641
Id = {GUID value}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Schedule\
TaskCache\Tree\Opera scheduled Autoupdate 4086469641
Index = 3

Information Theft

This Trojan gathers the following information on the affected computer:

  • Computer name
  • OS version
  • Volume serial number

Other Details

This Trojan connects to the following URL(s) to check for an Internet connection:

  • http://www.msftncsi.com/ncsi.txt

It connects to the following website to send and receive information:

  • http://{BLOCKED}tunrev.top/
  • http://{BLOCKED}kabenmen.net/
  • http://{BLOCKED}lili.top/
  • http://{BLOCKED}si11.top/
  • http://{BLOCKED}tynuu.top/
  • http://{BLOCKED}y.top/
  • http://{BLOCKED}eregulita.net/

It does the following:

  • It performs several checks before performing its malicious routines:
    • The following flags of its PEB structure must not indicate that it is being debugged:
      • BeingDebugged
      • NtGlobalFlag
    • Module filename must not contain the string "sample"
    • Volume serial number should not be:
      • 0xCD1A40 (ThreatExpert)
      • 0x70144646 (Malwr)
    • Registry data under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Disk\Enum must not contain the following strings:
      • qemu
      • virtual
      • vmware
      • xen
      • fffcce24 (VBox)
    • The following modules should not be loaded:
      • dbghelp
      • sbiedll
  • It terminates other programs related to process and network monitoring, and debugging.

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.344.06
FIRST VSAPI PATTERN DATE: 27 Jun 2018
VSAPI OPR PATTERN File: 14.345.00
VSAPI OPR PATTERN Date: 28 Jun 2018

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree
    • Opera scheduled Autoupdate 4086469641
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks
    • {GUID value}

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Application Data%\Microsoft\Windows\{Random1}

Step 6

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Startup%\{Random1}.lnk
  • %System%\Tasks\Opera scheduled Autoupdate 4086469641

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_SHARIK.WIL. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


Did this description help? Tell us how we did.