Analysis by: Nikko Tamana

ALIASES:

Mal/VBDoc-A (Sophos), W32/Swisyn.BVPZ!tr (Fortinet), Trojan.Win32.Swisyn (Ikarus), Trojan.Win32.Swisyn.bvpz (Kaspersky), Trojan:Win32/Comame (Microsoft), Win32/AutoRun.VB.AMZ worm (NOD32), W32.SillyFDC (Norton)

 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:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Propagates via removable drives, Downloaded from the Internet, Dropped by other malware

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

It drops copies of itself in all removable and physical drives found in the system. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It terminates if the said processes exist. This is to ensure that it runs uninterrupted on the affected system. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 360,469 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 19 Feb 2013
Payload: Connects to URLs/IPs, Compromises system security, Downloads files, Steals information

Arrival Details

This worm arrives via removable drives.

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

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft Office Outlook = "%System Root%\'\'\csrss.exe"

Propagation

This worm creates the following folder in all physical and removable drives:

  • '

It drops copies of itself in all removable and physical drives found in the system.

It drops the following copy(ies) of itself in all removable drives:

  • {Removable Drive}:\Assignments.exe
  • {Removable Drive}:\Business Ideas.exe
  • {Removable Drive}:\Softwares Keys.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

;{garbage code}
[Autorun]
;{garbage code}
Open= '\csrss.exe
;{garbage code}
shell\Open\Command= '\csrss.exe
;{garbage code}
shell\Explore\command= '\csrss.exe
;{garbage code}

Process Termination

This worm terminates the following processes if found running in the affected system's memory:

  • avguard.exe
  • avp.exe
  • afwserv.exe

Download Routine

This worm connects to the following website(s) to download and execute a malicious file:

  • http://www.{BLOCKED}c.co.cc/backups/sql.zip

Other Details

This worm terminates if the said processes exist. This is to ensure that it runs uninterrupted on the affected system.

However, as of this writing, the said sites are inaccessible.

NOTES:

It drops the following copies on its created folders in all physical and removable drives:

  • %System Drive%\'\'\csrss.exe
  • {Physical Drive}:\'\csrss.exe
  • {Removable Drive}:\'\csrss.exe

Its created folders have no icon.

The dropped AUTORUN.inf file attributes are hidden, system and read-only.

The {garbage code} in its dropped autorun.inf files are random generated and are being changed from time to time as long as WORM_VBNA.WPD is running.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.750.06
FIRST VSAPI PATTERN DATE: 24 Feb 2013
VSAPI OPR PATTERN File: 9.751.00
VSAPI OPR PATTERN Date: 25 Feb 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 WORM_VBNA.WPD

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
    • Microsoft  Office  Outlook = "%System Root%\'\'\csrss.exe"

Step 5

Search and delete AUTORUN.INF files created by WORM_VBNA.WPD that contain these strings

[ Learn More ]
  • ;{garbage code}
  • [Autorun]
  • ;{garbage code}
  • Open= '\csrss.exe
  • ;{garbage code}
  • shell\Open\Command= '\csrss.exe
  • ;{garbage code}
  • shell\Explore\command= '\csrss.exe
  • ;{garbage code}

Step 6

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.
  • {Physical Drive}:\'
  • {Removable Drive}:\'

Step 7

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