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TROJ_ZBOT.YUYACC

June 06, 2015
 Modified by: Sammy Chua
 ALIASES:

Trojan:Win32/Dynamer!ac (Microsoft); Trojan-Spy.Win32.Zbot.kyc (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Crypt4.AIIR (AVG)

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

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

307,712 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

29 May 2015

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.

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
{random key 1}

HKEY_CURRENT_USER\Software\Microsoft\
{random key 2}

HKEY_CURRENT_USER\Software\Microsoft\
{random key 3}

HKEY_CURRENT_USER\Software\Microsoft\
{random key 4}

HKEY_CURRENT_USER\Software\Microsoft\
{random key 5}

HKEY_CURRENT_USER\Software\Microsoft\
{random key 6}

Dropping Routine

This Trojan drops the following files:

  • %Application Data%\{existing folder 1}\{existing folder 2}\{existing folder 3}\{random file name 1}.{random extension 1}
  • %Application Data%\{existing folder 1}\{existing folder 2}\{existing folder 3}\{random file name 2}.{random extension 2}
  • %Application Data%\{existing folder 1}\{existing folder 2}\{existing folder 3}\{random file name 3}.exe
  • %User Temp%\tmp{random 4}.bat

(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.. %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.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}x.ru/
  • http://{BLOCKED}yincorp.com/server1/xxx1.jpg
  • http://www.{BLOCKED}x.ru/
  • http://{BLOCKED}yincorp.com/server1/xxx2.jpg
  • http://{BLOCKED}yincorp.com/server1/xxx3.jpg

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.684.06

FIRST VSAPI PATTERN DATE:

22 May 2015

VSAPI OPR PATTERN File:

11.685.00

VSAPI OPR PATTERN Date:

23 May 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

Search and delete these components

[ Learn More ]
There may be some components 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 Temp%\tmp{random 4}.bat

Step 3

Scan your computer with your Trend Micro product to delete files detected as TROJ_ZBOT.YUYACC. 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.

Step 4

The following created files/folders/registry keys/registry entries cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present system information with a backup. Note that the said components do not have to be deleted since it won't be harmful to the system.

  • %Application Data%\{existing folder 1}\{existing folder 2}\{existing folder 3}\{random file name 1}.{random extension 1}
  • %Application Data%\{existing folder 1}\{existing folder 2}\{existing folder 3}\{random file name 2}.{random extension 2}
  • %Application Data%\{existing folder 1}\{existing folder 2}\{existing folder 3}\{random file name 3}.exe
  • http://yandex.ru/
  • http://technologyincorp.com/server1/xxx1.jpg
  • http://www.yandex.ru/
  • http://technologyincorp.com/server1/xxx2.jpg
  • http://technologyincorp.com/server1/xxx3.jpg
  • HKEY_CURRENT_USER\Software\Microsoft\{random key 1}
  • HKEY_CURRENT_USER\Software\Microsoft\{random key 2}
  • HKEY_CURRENT_USER\Software\Microsoft\{random key 3}
  • HKEY_CURRENT_USER\Software\Microsoft\{random key 4}
  • HKEY_CURRENT_USER\Software\Microsoft\{random key 5}
  • HKEY_CURRENT_USER\Software\Microsoft\{random key 6}


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