Analysis by: Kathleen Notario
 Modified by: Michael Cabel
ALIASES:

Trojan.Carberp (Symantec); TrojanDownloader:Win32/Carberp.C (Microsoft); Trojan-Spy.Win32.Carberp.bnv (Kaspersky); Downloader.a!yw (Mcafee); Troj/Carberp-L (Sophos)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 REPORTED INFECTION:
 SYSTEM IMPACT RATING:
 INFORMATION EXPOSURE:

  • Threat Type: Spyware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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

It also has rootkit capabilities, which enables it to hide its processes and files from the user.

It modifies the Internet Explorer Zone Settings.

It connects to certain websites to send and receive information. It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 215,040 bytes
Memory Resident: Yes
Initial Samples Received Date: 23 Nov 2011
Payload: Downloads files

Arrival Details

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

  • %User Startup%\igfxtray.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 drops the following non-malicious file:

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

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

It adds the following processes:

  • explorer.exe
  • svchost.exe

It creates the following folders:

  • %System Root%\{random folder name}
  • %User Profile%\Application Data\MicroST

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

Other System Modifications

This spyware adds the following registry entries:

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

Rootkit Capabilities

This spyware also has rootkit capabilities, which enables it to hide its processes and files from the user.

Web Browser Home Page and Search Page Modification

This spyware modifies the Internet Explorer Zone Settings.

Other Details

This spyware connects to the following website to send and receive information:

  • http://{BLOCKED}icgamers.com

It deletes the initially executed copy of itself

NOTES:

This spyware may be downloaded from any of the following links contained in email messages spammed by malicious users:

  • http://{BLOCKED}.18.186.nw.nuvox.net/mozilla-firefox/rfstiwyz
  • http://{BLOCKED}.18.186.nw.nuvox.net/mozilla-firefox/4xe6ypev
  • http://{BLOCKED}.18.186.nw.nuvox.net/mozilla-firefox/4rf1y78z

This spammed email, supposed to download an installer of Firefox 8, contains the aforementioned links to download this malware. It may look like the following:

It injects codes into its created processes.

It downloads the following files from its C&C server to aid in its routines:

  • miniav.plug - remove certain malware from the affected system
  • passw.plug - steal user credentials
  • stopav.plug - disable antivirus applications installed on the affected system

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.594.09
FIRST VSAPI PATTERN DATE: 23 Nov 2011

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

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 4

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}
  • %User Profile%\Application Data\MicroST

Step 5

Reset Internet security settings

[ Learn More ]

Step 6

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