TROJ_REFROSO.AU
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Trojan
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.
TECHNICAL DETAILS
135,168 bytes
EXE
Yes
06 Nov 2009
Connects to URLs/IPs, Downloads files, Drops files
Arrival Details
This Trojan 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 Trojan drops the following copies of itself into the affected system:
- %System Root%\RECYCLER\S-1-5-21-9165828484-4458904799-977774283-9832\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\S-1-5-21-9165828484-4458904799-977774283-9832
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It injects threads into the following normal process(es):
- EXPLORER.EXE
It terminates itself if it finds the following processes in the affected system's memory:
- Process Monitor
- File Monitor
- Registry Monitor
- WireShark
Autostart Technique
This Trojan 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\S-1-5-21-9165828484-4458904799-977774283-9832\rundll32.exe"
Download Routine
This Trojan then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.
NOTES:
It connects to a remote site to dowload a file. However, the URL where the malware will connect is not in the malware body.
SOLUTION
9.200
6.608.03
06 Nov 2009
6.609.00
10 Nov 2009
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
Identify and delete files detected as TROJ_REFROSO.AU using either the Startup Disk or Recovery Console
Step 3
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\S-1-5-21-9165828484-4458904799-977774283-9832\rundll32.exe"
- Taskman = "%System Root%\RECYCLER\S-1-5-21-9165828484-4458904799-977774283-9832\rundll32.exe"
Step 4
Search and delete this folder
- %System Root%\RECYCLER\S-1-5-21-9165828484-4458904799-977774283-9832
Step 5
Scan your computer with your Trend Micro product to delete files detected as TROJ_REFROSO.AU. 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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