Analysis by: Mark Joseph Manahan
ALIASES:

TrojanDownloader:Win32/Carberp.C (Microsoft), Backdoor.Win32.Gbot.wbd (Kaspersky), Downloader.a!bvn (McAfee), Win32/TrojanDownloader.Carberp.AD trojan (Eset), Trojan.Carberp (Symantec)

 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:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This backdoor 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: 277,504 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 29 Nov 2012

Arrival Details

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

  • %User Startup%\igfxtray.exe
  • %User Startup%\{random filename}.exe

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

It creates the following folders:

  • %System Root%\{random foldername}
  • %System Root%\{random foldername}\{random foldername}

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet\Explorer\Main
TabProcGrowth = "0"

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}y.in
  • {BLOCKED}stemdwersfssnk.com
  • {BLOCKED}anksystem.ru
  • http://{BLOCKED}t-dbo.ru/s.dll

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.558.04
FIRST VSAPI PATTERN DATE: 29 Nov 2012
VSAPI OPR PATTERN File: 9.559.00

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

Restart in Safe Mode

[ Learn More ]

Step 3

Scan your computer with your Trend Micro product and note files detected as BKDR_CARBERP.C

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\Internet\Explorer\Main
    • TabProcGrowth = "0"

Step 5

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.
  • %System Root%\{random folder name}
  • %System Root%\{random folder name}\{random folder name}

Step 6

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.
  • %User Startup%\igfxtray.exe
  • %User Startup%\{random filename}.exe

Step 7

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