TROJ_DROPPER.FVZ
TrojanDropper:Win32/Zegost.B (Microsoft), Trojan.Gen (Symantec), Generic Dropper!dht (McAfee), Trojan.Win32.Agent.ddpg (Kaspersky)
Windows 2000, XP, Server 2003

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.
It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats.
TECHNICAL DETAILS
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 files:
- %System Root%\Documents and Settings\All Users\Application Data\Storm\update\%SESSIONNAME%\cenmu.cc3
- %User Temp%\hsrccexskf.dat
- %System%\e22a4301.rdb
(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.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)
It creates the following folders:
- %System Root%\Documents and Settings\All Users\Application Data\Storm\update\%SESSIONNAME%
Autostart Technique
This Trojan registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70
Type = "20"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70
Start = "2"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70
ErrorControl = "0"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70
ImagePath = "%SystemRoot%\system32\svchost.exe -k netsvcs"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70
DisplayName = "Messenger"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70
ObjectName = "LocalSystem"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70
Description = "Transmits net send and Alerter service messages between clients and servers. This service is not related to Windows Messenger. If this service is stopped, Alerter messages will not be transmitted. If this service is disabled, any services that explicitly depend on it will fail to start."
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70\Parameters
seRVicemAIN = "BuildTrusteeWithSidA"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70\Parameters
seRVicedlL = "%System Root%\Documents and Settings\All Users\Application Data\Storm\update\%SESSIONNAME%\cenmu.cc3"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70\Parameters
module = "%System Root%\cubxdjsupj"
It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Commessenger70
Other System Modifications
This Trojan adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Messenger
FailureActions = "{random values}"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Messenger
Group = ""
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Messenger\Parameters
seRVicemAIN = "BuildTrusteeWithSidA"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Messenger\Parameters
module = "%System Root%\cubxdjsupj"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Messenger
Start = "2"
(Note: The default value data of the said registry entry is 4.)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Messenger
ErrorControl = "0"
(Note: The default value data of the said registry entry is 1.)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Messenger\Parameters
ServiceDll = "%System Root%\Documents and Settings\All Users\Application Data\Storm\update\%SESSIONNAME%\cenmu.cc3"
(Note: The default value data of the said registry entry is %SystemRoot%\System32\msgsvc.dll.)
Download Routine
This Trojan connects to the following malicious URLs:
- {BLOCKED}14.3322.org:18188
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
Restart in Safe Mode
Step 3
Delete this registry key
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
- Commessenger70
- Commessenger70
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\Messenger
- FailureActions = "{random values}"
- FailureActions = "{random values}"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Messenger
- Group = ""
- Group = ""
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Messenger\Parameters
- seRVicemAIN = "BuildTrusteeWithSidA"
- seRVicemAIN = "BuildTrusteeWithSidA"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Messenger\Parameters
- module = "%System Root%\cubxdjsupj"
- module = "%System Root%\cubxdjsupj"
Step 5
Restore this modified 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\Messenger
- From: Start = "2"
To: Start = "4"
- From: Start = "2"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Messenger
- From: ErrorControl = "0"
To: ErrorControl = "1"
- From: ErrorControl = "0"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Messenger\Parameters
- From: ServiceDll = "%System Root%\Documents and Settings\All Users\Application Data\Storm\update\%SESSIONNAME%\cenmu.cc3"
To: ServiceDll = "%SystemRoot%\System32\msgsvc.dll"
- From: ServiceDll = "%System Root%\Documents and Settings\All Users\Application Data\Storm\update\%SESSIONNAME%\cenmu.cc3"
Step 6
Search and delete this folder
Step 7
Search and delete these files
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DROPPER.FVZ. 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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