TROJ_ZLOB.FN
TrojanDownloader:Win32/Zlob (Microsoft); Trojan.Zlob (Symantec); Trojan-Downloader.Win32.Zlob.hn (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Generic.Zlob.D4B1F8DF (FSecure)
Windows 2000, Windows XP, Windows 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 modifies files, disabling programs and applications from properly running.
TECHNICAL DETAILS
122,880 bytes
EXE
No
18 May 2012
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.
Autostart Technique
This Trojan registers itself as a BHO to ensure its automatic execution every time Internet Explorer is used by adding the following registry keys:
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{4da4616d-7e6e-4fd9-a2d5-b6c535733e22}
Other System Modifications
This Trojan modifies the following files:
- %User Profile%\Application Data\Microsoft
(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)
It adds the following registry keys:
HKEY_CLASSES_ROOT\CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}
HKEY_CLASSES_ROOT\CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}\
InprocServer32
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\Curre\ntVersion\
Explorer\{random key}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
explorer\run
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objecta\{4da4616d-7e6e-4fd9-a2d5-b6c535733e22}
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Search
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}\InprocServer32
ThreadingModel = "Apartment"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
explorer\run
nvctrl.exe = "nvctrl.exe"
It modifies the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Start Page = "about:blank"
(Note: The default value data of the said registry entry is http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome.)
Dropping Routine
This Trojan drops the following files:
- %System%\hpAB34.tmp
- %System%\ncompat.tlb
- %User Profile%\Microsoft\Crypto
- %User Profile%\Crypto\RSA
- %User Profile%\RSA\S-1-5-21-4025279379-4087772427-2915903831-500
- %System%\msvol.tlb
(Note: %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.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)
This report is generated via an automated analysis system.
SOLUTION
9.200
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
Close all opened browser windows
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_CLASSES_ROOT\CLSID
- {4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}
- In HKEY_CLASSES_ROOT\CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}
- InprocServer32
- In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Curre\ntVersion\Explorer
- {random key}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\explorer
- run
- In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objecta
- {4da4616d-7e6e-4fd9-a2d5-b6c535733e22}
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
- Search
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\Classes\CLSID\{4DA4616D-7E6E-4FD9-A2D5-B6C535733E22}\InprocServer32
- ThreadingModel = "Apartment"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\explorer\run
- nvctrl.exe = "nvctrl.exe"
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_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- From: Start Page = "about:blank"
To: Start Page = ""http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome""
- From: Start Page = "about:blank"
Step 6
Search and delete these files
- %System%\hpAB34.tmp
- %System%\ncompat.tlb
- %User Profile%\Microsoft\Crypto
- %User Profile%\Crypto\RSA
- %User Profile%\RSA\S-1-5-21-4025279379-4087772427-2915903831-500
- %System%\msvol.tlb
Step 7
Scan your computer with your Trend Micro product to delete files detected as TROJ_ZLOB.FN. 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.
Step 8
Restore deleted/modified files and/or registry entries from backup
*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.
- %User Profile%\Application Data\Microsoft
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