Analysis by: Jaime Benigno Reyes
 Modified by: Rika Joi Gregorio
ALIASES:

TrojanDownloader:Win32/Dofoil.T(Microsoft), Trojan.Smoaler(Symantec), Trojan-Downloader.Win32.Dofoil(Sunbelt), Win32/Pronny.LZ worm(Eset)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 84,055 bytes
Memory Resident: Yes
Initial Samples Received Date: 02 Sep 2014
Payload: Connects to URLs/IPs

Arrival Details

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

  • %Application Data%\{random folder name}\{random file name}.exe

(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 creates the following folders:

  • %Application Data%\{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 injects codes into the following process(es):

  • svchost.exe

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random name} = "%Application Data%\{random folder name}\{random file name}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
{random name} = "%Application Data%\{random folder name}\{random file name}.exe"

Other Details

This Trojan deletes the initially executed copy of itself

NOTES:

It connects to the URLs that are found in the registry entries of all registry subkeys under this registry key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall

It terminates itself once it is executed in the following virtual environments:

  • sbiedll
  • dbghelp
  • qemu
  • virtual
  • vmware

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 11.144.03
FIRST VSAPI PATTERN DATE: 12 Sep 2014
VSAPI OPR PATTERN File: 11.145.00
VSAPI OPR PATTERN Date: 13 Sep 2014

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

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 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
    • {random name} = "%Application Data%\{random folder name}\{random file name}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • {random name} = "%Application Data%\{random folder name}\{random file name}.exe"

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%\{random folder name}

Step 6

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