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BKDR_PUSHDO.IMA

July 24, 2014
 Analysis by: Vincent Martin Hermosura
 ALIASES:

Trojan.Win32.Cutwail.deo (Kaspersky), TrojanDownloader:Win32/Cutwail (Microsoft), Backdoor.Trojan (Norton), PWSZbot-FAAB!EA19C30C23FC (Nai), Win32.Malware!Drop (Sunbelt), TR/Crypt.EPACK.21550 (Antivir), Trojan.GenericKD.1740135 (Bitdefender), W32/Cutwail.DEO!tr (Fortinet), Trojan.Win32.Cutwail (Ikarus), Win32/Wigon.PH trojan (Nod32), Trj/Chgt.C (Panda)

 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: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

165,376 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Jul 2014

Payload:

Compromises system security

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 Profile%\{random filename}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random filename} = "%User Profile%\{random filename}.exe"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
AppManagement = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
{random filename}zap = "{random values}"

Propagation

This backdoor uses any of the following Simple Mail Transfer Protocol (SMTP) servers:

  • mail.airmail.net
  • smtp.compuserve.com
  • smtp.directcon.net
  • smtp.live.com
  • smtp.mail.yahoo.com
  • smtp.sbcglobal.yahoo.com

Backdoor Routine

This backdoor may also compose messages that can be part of its spamming routine.

It executes the following commands from a remote malicious user:

  • Download and execute files
  • Get OS Version
  • Get System Information
  • Get Network Information
  • Retrieve Spam Configuration/Content

NOTES:

It performs random GET Request connection to the certain URLs to mask outbound connections.

It performs random POST Request connection to the certain URLs to mask outbound connections.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.938.06

FIRST VSAPI PATTERN DATE:

03 Jul 2014

VSAPI OPR PATTERN File:

10.939.00

VSAPI OPR PATTERN Date:

03 Jul 2014

Step 1

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 2

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 3

Scan your computer with your Trend Micro product and note files detected as BKDR_PUSHDO.IMA

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

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\Windows\CurrentVersion\Run
    • {random filename} = "%User Profile%\{random filename}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • AppManagement = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • {random filename}zap = "{random values}"

Step 6

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

Step 7

The following created files/folders/registry keys/registry entries cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present system information with a backup. Note that the said components do not have to be deleted since it won't be harmful to the system.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random filename} = "%User Profile%\{random filename}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • AppManagement = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • {random filename}zap = "{random values}"


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