Analysis by: Jimelle Monteser
ALIASES:

TrojanDownloader:Win32/Upatre.A (Microsoft), Win32/TrojanDownloader.Small.AAB trojan (NOD32)

 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: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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

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

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 26,642 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 09 Oct 2013
Payload: Connects to URLs/IPs, Downloads files

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.

Installation

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

  • %User Temp%\gewos.exe

(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.)

Download Routine

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

  • http://{BLOCKED}p.net/config/8mo.exe:443

It saves the files it downloads using the following names:

  • %User Temp%\gewosik.exe - detected as TSPY_ZBOT.VCC

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

Other Details

This Trojan deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.330.04
FIRST VSAPI PATTERN DATE: 09 Oct 2013
VSAPI OPR PATTERN File: 10.331.00
VSAPI OPR PATTERN Date: 10 Oct 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 dropped/downloaded by TROJ_UPATRE.ZBT. (Note: Please skip this step if the threats listed below have already been removed.)

Step 3

Scan your computer with your Trend Micro product to delete files detected as TROJ_UPATRE.ZBT. 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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