Analysis by: Rika Joi Gregorio
ALIASES:

TrojanDownloader:Win32/Umbald.A(Microsoft), Trojan-Downloader.Win32.Andromeda(Ikarus)

 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: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size: 502,272 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 07 Aug 2013

Arrival Details

This worm 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 worm drops the following copies of itself into the affected system and executes them:

  • %Windows%\winsvchost.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Pdf Updater = ""%Windows%\winsvchost.exe""

Other System Modifications

This worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
rJm3lrm1

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • {drive letter}:\starter.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[autorun]
open=starter.exe

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}l.{BLOCKED}dican.com/Panel/bot.php

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.202.05
FIRST VSAPI PATTERN DATE: 07 Aug 2013
VSAPI OPR PATTERN File: 10.203.00
VSAPI OPR PATTERN Date: 08 Aug 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

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.

 
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
    • rJm3lrm1

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Pdf Updater = ""%Windows%\winsvchost.exe""

Step 5

Search and delete AUTORUN.INF files created by WORM_UMBALD.AD that contain these strings

[ Learn More ]


[autorun]
open=starter.exe

Step 6

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