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WORM_SKYDLL.A

March 27, 2015
 ALIASES:

IM-Flooder.Win32.Skyper.p (Kaspersky); Worm:Win32/SkyDll.A (Microsoft);

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via instant messaging applications

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites. It may be manually installed by a user.

  TECHNICAL DETAILS

File Size:

2,520,226 bytes

File Type:

EXE

Memory Resident:

Yes

Payload:

Downloads files

Arrival Details

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

It may be manually installed by a user.

Installation

This worm adds the following folders:

  • %Application Data%\{random name 0}
  • %Program Files%\{random name 1}

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

Autostart Technique

This worm registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKLM\SYSTEM\ControlSet001\
Services\{random hex}
ImagePath = "%System%\rundll32.exe" "%Program Files%\{random name 1}\{random name 1}.dll",serv

HKLM\SYSTEM\ControlSet001\
Services\{random hex}
DisplayName = {random name 1}

Other Details

This worm drops the following file(s)/component(s):

  • %Application Data%\{random name 0}\{random name 0}.exe
  • %Application Data%\{random name 0}\{random name 1}_{random numbers}.dll
  • %Application Data%\{random name 0}\unins000.dat
  • %Application Data%\{random name 0}\unins000.exe
  • %Program Files%\{random name 1}\{random name 1}.dll

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

NOTES:

Once executed, it searches for the following processes if running in the system:

  • skype.exe

It may be used as a component to send a message to the user's contacts containing a link where copies of other malware can be downloaded:

  • {BLOCKED}videoskype.com
  • {BLOCKED}eskype.com
  • {BLOCKED}eskype.net
  • {BLOCKED}skype.net
  • {BLOCKED}nskype.net
  • {BLOCKED}pskype.net

Message sent via Skype:

  • {message} {contact name} video: http://{URL List}/?n={contact name}

Once clicked, the link leads to this URL:

  • http://{URL List}/?n={contact name}

Users are tricked into clicking the 'Play' button to view the video:

They are then led to install a plugin in order to play the video:

A malicious file is downloaded, which users may execute and install. The installer may or may not prompt a GUI:

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.526.04

FIRST VSAPI PATTERN DATE:

08 Mar 2015

VSAPI OPR PATTERN File:

11.527.00

VSAPI OPR PATTERN Date:

08 Mar 2015

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 key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • HKLM\SYSTEM\ControlSet001\Services\{random hex}

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 name 0}\{random name 0}.exe
  • %Application Data%\{random name 0}\{random name 1}_{random numbers}.dll
  • %Application Data%\{random name 0}\unins000.dat
  • %Application Data%\{random name 0}\unins000.exe
  • %Program Files%\{random name 1}\{random name 1}.dll

Step 6

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