W2KM_POWMET.CAE

 Analysis by: Byron Jon Gelera

 ALIASES:

W97M.Downloader (Symantec)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It employs registry shell spawning by adding certain registry entries. This allows this malware to execute even when other applications are opened.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size:

39,424 bytes

File Type:

DOC

Memory Resident:

No

Initial Samples Received Date:

23 Jan 2017

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

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

Autostart Technique

This Trojan employs registry shell spawning to ensure its execution when certain file types are accessed by adding the following entries:

HKEY_CURRENT_USER\Software\Classes\
mscfile\shell\open\
command
{default} = %User Temp%\puttyx86.exe

Download Routine

This Trojan saves the files it downloads using the following names:

  • %User Temp%\puttyx86.exe

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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 then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}cro.com/cli/Apple%20Inc.exe

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

13.174.04

FIRST VSAPI PATTERN DATE:

23 Jan 2017

VSAPI OPR PATTERN File:

13.175.00

VSAPI OPR PATTERN Date:

24 Jan 2017

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

Restore this modified registry value

[ 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_CURRENT_USER\Software\Classes\mscfile\shell\open\command
    • From: {Default} = %User Temp%\puttyx86.exe
      To: {Default} = %SystemRoot%\system32\mmc.exe "%1" %*

Step 5

Search and delete these files

[ 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.

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as W2KM_POWMET.CAE. 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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