Analysis by: Mar Philip Elaurza
ALIASES:

Trojan.Win32.Fsysna.auzf (KASPERSKY), Worm:Win32/Folxrun!rfn (MICROSOFT), W32.SillyFDC (NORTON)

 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: Dropped by other malware, Downloaded from the Internet, Via physical/removable drives

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

It steals system information.

  TECHNICAL DETAILS

File Size: 262,144 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 16 Sep 2015
Payload: Steals information, Drops files, Displays windows

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.

Installation

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

  • %User Temp%\explorer.exe

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

It terminates the execution of the copy it initially executed and executes the copy it drops instead.

Autostart Technique

This worm drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\msfold.exe

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Propagation

This worm searches for folders in all physical and removable drives then drops copies of itself inside the folder as {folder name}.EXE.

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

  • {Removable Drive Letters}:\kabe.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:

[AutoRun]
action=Open
shellexecute=kabe.bat
shell\explore\command=kabe.bat
USEAUTOPLAY=1
shell\Open\command=kabe.bat
shell\Autorun\command=kabe.bat
shell\Search\command=kabe.bat

Dropping Routine

This worm drops the following files:

  • %User Temp%\sajith_and_rasini.db
  • %User Temp%\i_love_you_rasini.db

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

Information Theft

This worm steals system information.

Other Details

This worm displays a pop-up window with the following message:

Your Desktop is locked now !

NOTES:

It locks the desktop and ask for users to email and pay the cybercriminals for the unlock code.

The following messages are seen on the locked desktop:


Email {BLOCKED}ix@hotmail.com
Send Email to our team and pay 4$ for unlock code
together with the textbox and button for unlock.

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.918.07
FIRST VSAPI PATTERN DATE: 14 Sep 2015
VSAPI OPR PATTERN File: 11.919.00
VSAPI OPR PATTERN Date: 15 Sep 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

Search and delete AUTORUN.INF files created by WORM_RASITH.A that contain these strings

[ Learn More ]
[AutoRun]
action=Open
shell\execute=kabe.bat
shell\explore\command=kabe.bat
USEAUTOPLAY=1
shell\Open\command=kabe.bat
shell\Autorun\command=kabe.bat
shell\Search\command=kabe.bat

Step 5

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Startup%\msfold.exe
  • %User Temp%\sajith_and_rasini.db
  • %User Temp%\i_love_you_rasini.db

Step 6

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