Analysis by: Sabrina Lei Sioting
ALIASES:

Trojan:Win32/Alureon.DV [Microsoft]; Backdoor.Win32.Agent.avko [Kaspersky]; Trojan-Dropper.Win32.Agent [Ikarus]; Win32/Olmarik.YR trojan [Nod32];

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • 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.

  TECHNICAL DETAILS

File Size: 75,264 bytes
File Type: EXE
Initial Samples Received Date: 03 Jun 2010

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:

  • %System%\{random}.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

This Trojan registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347
NextInstance = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347\
0000
Service = "MSWU-b04ba347"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347\
0000
Legacy = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347\
0000
ConfigFlags = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347\
0000
Class = "LegacyDriver"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347\
0000
ClassGUID = "{8ECC055D-047F-11D1-A537-0000F8753ED1}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347\
0000
DeviceDesc = "MSWU-b04ba347"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSWU-b04ba347
Type = "10"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSWU-b04ba347
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSWU-b04ba347
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSWU-b04ba347
ImagePath = "%System%\{random}.exe"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSWU-b04ba347
DisplayName = "MSWU-b04ba347"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSWU-b04ba347
ObjectName = "LocalSystem"

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MSWU-B04BA347\
0000

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\MSWU-b04ba347

Dropping Routine

This Trojan drops the following files:

  • %System%\spool\prtprocs\w32x86\{random}.dll

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 7.216.15
FIRST VSAPI PATTERN DATE: 03 Jun 2010
VSAPI OPR PATTERN File: 7.217.00
VSAPI OPR PATTERN Date: 04 Jun 2010

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

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.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
    • LEGACY_MSWU-B04BA347
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • MSWU-b04ba347

Step 3

Search and delete these files

[ Learn More ]
There may be some component 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. %System%\spool\prtprocs\w32x86\{random}.dll

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_ZLOB.FYB. 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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