Analysis by: Jaime Benigno Reyes

ALIASES:

TrojanDownloader:Win32/Thoper.B (Microsoft), Trojan.FakeAV (Symantec), Trojan.Win32.Agent.iaql (Kaspersky), Artemis!9D7DC7CC808C (McAfee)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites. It may be downloaded by other malware/grayware from remote sites.

It does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size: 74,752 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 27 Aug 2013
Payload: Collects system information

Arrival Details

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

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

  • JS_NISEILY.AB

It may be downloaded from the following remote site(s):

  • http://downfile2.{BLOCKED}arecenter.com/virtual/news/mm.exe

Installation

This backdoor drops the following copies of itself into the affected system and executes them:

  • %All Users Profile%\taskeng.exe

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

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

  • QF-2-0-33

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
taskeng = "%All Users Profile%\taskeng.exe"

Other System Modifications

This backdoor adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
LOG
CLSID = "{hex values}"

It adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
LOG

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
LOGPROXY

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

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

  • download arbitrary files
  • perform remote shell commands
  • get system information
  • create directories

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

  • http://kitamura.{BLOCKED}arecenter.com/{8 random hex values}FFFFFFFF.aspx

Information Theft

This backdoor gathers the following data:

  • computer name
  • user name
  • drive information
  • os version

NOTES:
This backdoor disables the firewall by executing in command prompt the line net stop SharedAccess.

It will only perform its malicious routine if the current year is 2013 and above.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.242.02
FIRST VSAPI PATTERN DATE: 27 Aug 2013
VSAPI OPR PATTERN File: 10.243.00
VSAPI OPR PATTERN Date: 28 Aug 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 BKDR_KORPLG.ILP

  • JS_NISEILY.AB

Step 3

Identify and terminate files detected as BKDR_KORPLG.ILP

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Delete this registry value

[ 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\CurrentVersion\Run
    • taskeng = "%All Users Profile%\taskeng.exe"

Step 5

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • HKEY_LOCAL_MACHINE\SOFTWARE\Classes\LOG
  • HKEY_LOCAL_MACHINE\SOFTWARE\Classes\LOGPROXY

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_KORPLG.ILP. 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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