PE_VASOR.A
W32/Vasor.b (McAfee); W32.Vasor (Symantec); Worm.Win32.Vasor.17400 (Kaspersky); BehavesLike.Win32.Malware.bsf (vs) (Sunbelt); Worm/Vasor (AVG)
Windows 2000, Windows XP, Windows Server 2003
Threat Type: File infector
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This file infector arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
TECHNICAL DETAILS
220,160 bytes
EXE
Yes
05 Jul 2013
Arrival Details
This file infector 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 file infector drops the following copies of itself into the affected system:
- %System Root%\RECYCLER\S-1-5-21-3623455640-1605238121-007859134-6157\MsMxEng.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:
- %User Temp%\Task
- %System Root%\RECYCLER
- %System Root%\RECYCLER\S-1-5-21-3623455640-1605238121-007859134-6157
(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
Autostart Technique
This file infector 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-1-5-21-3623455640-1605238121-007859134-6157\MsMxEng.exe"
Other System Modifications
This file infector adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%User Temp%\svchost.exe = "%User Temp%\svchost.exe:*:Enabled:Krosavcheg"
Dropping Routine
This file infector drops the following files:
- %User Temp%\svchost.exe
- %System Root%\RECYCLER\S-1-5-21-3623455640-1605238121-007859134-6157\Desktop.ini
(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
This report is generated via an automated analysis system.
SOLUTION
9.300
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
Identify and delete files detected as PE_VASOR.A 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-1-5-21-3623455640-1605238121-007859134-6157\MsMxEng.exe"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- %User Temp%\svchost.exe = "%User Temp%\svchost.exe:*:Enabled:Krosavcheg"
Step 4
Search and delete these components
- %User Temp%\svchost.exe
- %System Root%\RECYCLER\S-1-5-21-3623455640-1605238121-007859134-6157\Desktop.ini
Step 5
Search and delete these folders
- %User Temp%\Task
- %System Root%\RECYCLER
- %System Root%\RECYCLER\S-1-5-21-3623455640-1605238121-007859134-6157
Step 6
Scan your computer with your Trend Micro product to clean files detected as PE_VASOR.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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