Analysis by: Anthony Joe Melgarejo
ALIASES:

Trojan:Win32/Sisproc (Microsoft), Artemis!EBC7741E6E01 (McAfee), Backdoor.Trojan (Symantec)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Spyware

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This spyware may be downloaded by other malware/grayware from remote sites.

It executes then deletes itself afterward.

It executes commands from a remote malicious user, effectively compromising the affected system. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: Varies
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 21 Mar 2013
Payload: Connects to URLs/IPs, Drops files, Steals information

Arrival Details

This spyware may be downloaded by the following malware/grayware from remote sites:

  • TROJ_DLOAD.KRS

Infection Points

This spyware arrives as a file downloaded from the following URLs:

  • http://www.{BLOCKED}a.com/rgboard/data/skins/paper.gif

Installation

This spyware drops and executes the following files:

  • %User Temp%\w7e89.tmp - also detected as TSPY_INJECTO.KRS (deleted afterwards)
  • %System%\shellservice.exe - also detected as TSPY_INJECTO.KRS
  • %System%\themeservics.dll - also detected as TSPY_INJECTO.KRS
  • %User Temp%\SVCHOST.exe - detected as BKDR_AGENT.KSI

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %System% is the Windows system folder, which is usually C:\Windows\System32.)

It drops the following non-malicious files:

  • %Temp%\~tmp000.tmp
  • %Temp%\~tmp000.tmp~

(Note: %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp.)

It executes then deletes itself afterward.

It injects codes into the following process(es):

  • spoolsv.exe

Autostart Technique

This spyware modifies the following registry entry(ies) to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "explorer.exe,shellservice.exe"

(Note: The default value data of the said registry entry is "Explorer.exe".)

Backdoor Routine

This spyware executes the following commands from a remote malicious user:

  • Download and execute %User Temp%\13785.tmp
  • Remote shell
  • Set connection interval to the C&C server
  • Set number of connection attempts to the C&C server

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}a.co.kr/rgboard/rgboard/view_in.php

It posts the following information to its command and control (C&C) server:

  • Computer Name
  • Registered Owner
  • Registered Organization
  • OS Installation Date

However, as of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.812.03
FIRST VSAPI PATTERN DATE: 21 Mar 2013
VSAPI OPR PATTERN File: 9.813.00
VSAPI OPR PATTERN Date: 21 Mar 2013

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

Remove malware/grayware files that dropped/downloaded TSPY_INJECTO.KRS

     
    • TROJ_DLOAD.KRS

Step 3

Remove malware/grayware files dropped/downloaded by TSPY_INJECTO.KRS

    • BKDR_AGENT.KSI

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "explorer.exe,shellservice.exe"
      To: Shell = "Explorer.exe"

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.
  • %Temp%\13785.tmp
  • %Temp%\~tmp000.tmp
  • %Temp%\~tmp000.tmp~

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TSPY_INJECTO.KRS. 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.


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