WORM_REFROSO.WN
W32.IRCBot (Symantec); VirTool:Win32/Injector.gen!AD (Microsoft); Trojan-Downloader.Win32.Refroso.avp (Kaspersky); BackDoor-EEF (Mcafee)
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
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.
TECHNICAL DETAILS
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
SOLUTION
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Scan your computer with your Trend Micro product and note files detected as WORM_REFROSO.WN
Step 3
Restart in Safe Mode
Step 4
Delete this registry value
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- Taskman = %System Root%\RECYCLER\{SID}\rundll32.exe
Step 5
Search and delete these folders
%System Root%\RECYCLER\{SID}
Step 6
Search and delete AUTORUN.INF files created by WORM_REFROSO.WN that contain these 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
Step 7
Scan your computer with your Trend Micro product to delete files detected as WORM_REFROSO.WN. 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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