TROJ_DROPPER.WYAA

 Analysis by: Michael John Marcos

 ALIASES:

TrojanDownloader: Win32/Esaprof.A (Microsoft)

 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:

Downloaded from the Internet


This Trojan may be unknowingly downloaded by a user while visiting malicious websites.

It deletes files in certain folders, disabling programs and applications from properly running.

It does not have any propagation routine.

It does not have any backdoor routine.

  TECHNICAL DETAILS

File Size:

4,208,128 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

15 Jan 2015

Payload:

Downloads files

Arrival Details

This Trojan may be unknowingly downloaded by a user while visiting malicious websites.

Installation

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

  • %Start Menu%\Programs\{malware name}.exe

(Note: %Start Menu% is the Start Menu folder, where it usually is C:\Documents and Settings\{user name}\Start Menu on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu 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:

  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\0.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\1.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\2.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\3.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\4.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\~swd1.dat
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\~swd1.swf

(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 creates the following folders:

  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk

(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.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Startup = "%Start Menu%\Programs\{malware name}.exe"

Other System Modifications

This Trojan deletes files in the following folders:

  • %System Root%

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

It adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Speech\Voices

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}4.mass.hc.ru/test1.zip

It connects to the following URL(s) to download its configuration file:

  • http://www.{BLOCKED}ssess.ru/photo.txt?{random value}
  • http://www.{BLOCKED}tatist.ru/photo.txt?{random value}
  • http://{BLOCKED}swork.ru/test2.txt
  • http://{BLOCKED}swork.ru/test.txt

It saves the files it downloads using the following names:

  • %User Profile%\file2.exe

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

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

11.414.02

FIRST VSAPI PATTERN DATE:

15 Jan 2015

VSAPI OPR PATTERN File:

11.415.00

VSAPI OPR PATTERN Date:

15 Jan 2015

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

Restart in Safe Mode

[ Learn More ]

Step 3

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.

 
  • HKEY_CURRENT_USER\Software\Microsoft\Speech\Voices

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Startup = "%Start Menu%\Programs\{malware name}.exe"

Step 5

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.
  • %Start Menu%\Programs\{malware name}.exe
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\0.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\1.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\2.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\3.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\4.mdd
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\~swd1.dat
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk\~swd1.swf

Step 6

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.
  • %User Temp%\wrd-{random value}-{random value}-{random value}.~lk

Step 7

Remove malware/grayware files dropped/downloaded by TROJ_DROPPER.WYAA. (Note: Please skip this step if the threats listed below have already been removed.)

    • TROJ_CO.96FEE72C

Step 8

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