TROJ_DROPPER.MRX
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
Threat Type: Trojan
Destructiveness: No
Encrypted:
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.
TECHNICAL DETAILS
245,248 bytes
EXE
Yes
05 Feb 2013
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 and executes the following files:
- %User Temp%\{random}.tmp\msupdate.exe
- %User Temp%\{random}.tmp\PsExec.bat
- %User Temp%\{random}.tmp\PsExec.exe
(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.)
It creates the following folders:
- %User Temp%\{random}.tmp
(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.)
Other System Modifications
This Trojan creates the following registry entry(ies) to bypass Windows Firewall:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\SharedAccess\Parameters\
FirewallPolicy\FirewallRules
{GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=17|Profile=Public|App=%User Temp%\{random}.tmp\PsExec.exe|Name=enable|"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\SharedAccess\Parameters\
FirewallPolicy\FirewallRules
{GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=6|Profile=Public|App=%User Temp%\{random}.tmp\msupdate.exe|Name=enable|"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\SharedAccess\Parameters\
FirewallPolicy\FirewallRules
{GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=17|Profile=Public|App=%User Temp%\{random}.tmp\msupdate.exe|Name=enable|"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
services\SharedAccess\Parameters\
FirewallPolicy\FirewallRules
{GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|App=%Application Data%\{random folder name 1}\{random file name 1}.exe|Name=explore|"
NOTES:
The dropped files are deleted after successful execution.
SOLUTION
9.300
9.708.04
05 Feb 2013
9.709.00
06 Feb 2013
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
Scan your computer with your Trend Micro product and note files detected as TROJ_DROPPER.MRX
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\SYSTEM\CurrentControlSet\services\SharedAccess\Parameters\FirewallPolicy\FirewallRules
- {GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=6|Profile=Public|App=%User Temp%\{random}.tmp\PsExec.exe|Name=enable|"
- {GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=6|Profile=Public|App=%User Temp%\{random}.tmp\PsExec.exe|Name=enable|"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\SharedAccess\Parameters\FirewallPolicy\FirewallRules
- {GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=17|Profile=Public|App=%User Temp%\{random}.tmp\PsExec.exe|Name=enable|"
- {GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=17|Profile=Public|App=%User Temp%\{random}.tmp\PsExec.exe|Name=enable|"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\SharedAccess\Parameters\FirewallPolicy\FirewallRules
- {GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=6|Profile=Public|App=%User Temp%\{random}.tmp\msupdate.exe|Name=enable|"
- {GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=6|Profile=Public|App=%User Temp%\{random}.tmp\msupdate.exe|Name=enable|"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\SharedAccess\Parameters\FirewallPolicy\FirewallRules
- {GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=17|Profile=Public|App=%User Temp%\{random}.tmp\msupdate.exe|Name=enable|"
- {GUID} = "v2.10|Action=Allow|Active=TRUE|Dir=In|Protocol=17|Profile=Public|App=%User Temp%\{random}.tmp\msupdate.exe|Name=enable|"
Step 5
Search and delete this folder
- %User Temp%\{random}.tmp
Step 6
Search and delete the file detected as TROJ_DROPPER.MRX
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DROPPER.MRX. 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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