WORM_REFROSO.WN

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

It connects to a website to send and receive 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.

Installation

This worm drops the following non-malicious files:

• %System Root%\RECYCLER\{SID}\Desktop.ini

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

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

• %System Root%\RECYCLER\{SID}\rundll32.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It creates the following folders:

• %System Root%\RECYCLER\{SID}

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It injects itself into the following processes as part of its memory residency routine:

• explorer.exe

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = %System Root%\RECYCLER\{SID}\rundll32.exe

Propagation

This worm drops copies of itself in all removable drives.

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 characters}
[autorun
:jmp0
open={folder name}\{random filename}.exe
:nop
icon=%SystemRoot%\system32\SHELL32.dll,4
;{garbage characters}
action=Open folder to view files using Windows Explorer
;{garbage characters}
shell\\\open\\\command={folder name}/{random filename}.exe
shell\\explore\\\command={folder name}/{random filename}.exe
useautoplay=1
[AutoRun]
;{garbage characters}
:GOTO NUL

Backdoor Routine

This worm connects to the following websites to send and receive information:

• {BLOCKED}ws.org

Dropping Routine

This worm sets the attributes of its dropped file(s) to the following:

• Hidden
• Read Only
• System

NOTES:

It checks for the following:

• - if the malware filename is C:\sample.exe or C:\windows\system32\sample_1.exe
• - if the username is currentuser
• - if the following window names exist:
• The Wireshark Network Analyzer
• Process Monitor - Sysinternals: www.sysinternals.com
• File Monitor - Sysinternals: www.sysinternals.com
• Registry Monitor - Sysinternals: www.sysinternals.com