Analysis by: Jimelle Monteser
ALIASES:

Backdoor.Win32.Pushdo.qny (Kaspersky), TrojanDownloader:Win32/Cutwail.BS (Microsoft), Trojan-Downloader.Win32.Cutwail (Ikarus), W32/Pushdo.YOY!tr (Fortinet)

 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:

  • 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: 47,104 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 30 Jul 2013

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 adds the following folders:

  • %Application Data%\Microsoft\Crypto
  • %Application Data%\Microsoft\Crypto\RSA
  • %Application Data%\Microsoft\Crypto\RSA\{random folder name}

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

It drops the following copies of itself into the affected system:

  • %User Profile%\{malware file name}

(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
{malware file name} = "%User Profile%\{malware file name}"

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
{malware file name} = "{random values}"

Dropping Routine

This backdoor drops the following files:

  • %Application Data%\Microsoft\Crypto\RSA\{random folder name}\{random}

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

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}jovop.kz
  • http://{BLOCKED}usea.kz
  • http://{BLOCKED}shogz.kz
  • http://{BLOCKED}azofix.kz
  • http://{BLOCKED}nefim.kz
  • http://{BLOCKED}ncewiz.kz
  • http://{BLOCKED}vuz.kz
  • http://{BLOCKED}uwecb.kz
  • http://{BLOCKED}lof.kz
  • http://{BLOCKED}eopidu.kz
  • http://{BLOCKED}uzw.kz
  • http://{BLOCKED}hea.kz
  • http://{BLOCKED}qsurco.kz
  • http://{BLOCKED}alqu.kz
  • http://{BLOCKED}t.net
  • http://{BLOCKED}duqv.kz
  • http://{BLOCKED}eifove.kz
  • http://{BLOCKED}ufvib.kz
  • http://{BLOCKED}dav.kz
  • http://{BLOCKED}qogl.kz
  • http://{BLOCKED}kurm.kz
  • http://{BLOCKED}udo.kz
  • http://{BLOCKED}ihug.kz
  • http://{BLOCKED}nadj.kz
  • http://{BLOCKED}curc.kz
  • http://{BLOCKED}jososx.kz
  • http://{BLOCKED}ebhoh.kz

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.186.01
FIRST VSAPI PATTERN DATE: 30 Jul 2013
VSAPI OPR PATTERN File: 10.187.00
VSAPI OPR PATTERN Date: 31 Jul 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

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

Step 3

Restart in Safe Mode

[ Learn More ]

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\Windows\CurrentVersion\Run
    • {malware file name} = "%User Profile%\{malware file name}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • AppManagement = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • {malware file name} = "{random values}"

Step 5

Search and delete this folder

[ 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.
  • %Application Data%\Microsoft\Crypto

Step 6

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