BKDR_NFLOG.AU
Trojan:Win32/NfLog.A (Microsoft), Backdoor.Win32.Agent.dbff (Kaspersky)
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
This backdoor may be dropped by other malware.
It executes commands from a remote malicious user, effectively compromising the affected system.
It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.
TECHNICAL DETAILS
Arrival Details
This backdoor may be dropped by the following malware:
- TROJ_MDROP.ZPE
Installation
This backdoor drops the following file(s)/component(s):
- %Temp%\$NtUninstallKB942388$ - Contains stolen information
- %Temp%\NfIpv6.ocx - Also detected as BKDR_NFLOG.AU
- %Temp%\YahooCache.ini
(Note: %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp.)
It injects itself into the following processes as part of its memory residency routine:
- svchost.exe
Autostart Technique
This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP
Type = "20"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP
Start = "2"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP
ErrorControl = "1"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP
ImagePath = "%SystemRoot%\System32\svchost.exe -k netsvcs"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP
DisplayName = "IPv6 Stack Local Support"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP
ObjectName = "LocalSystem"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP
Description = "Net address translation for IPv6 Protocol."
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP\Parameters
ServiceDll = "{malware path and filename}"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP\Security
Security = "{hex values}"
Other System Modifications
This backdoor adds the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP\Parameters
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\IPRIP\Security
It adds the following registry entries:
HKEY_USERS\.DEFAULT\Software\
Microsoft\Clock
HID = "{hex values}"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths
Directory = "NetworkService's %Temporary Internet Files%\Content.IE5"
(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths\path1
CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache1"
(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5\Cache1.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths\path2
CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache2"
(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5\Cache2.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths\path3
CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache3"
(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5\Cache3.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
Cache\Paths\path4
CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache4"
(Note: The default value data of the said registry entry is %Temporary Internet Files%\Content.IE5\Cache4.)
Backdoor Routine
This backdoor executes the following commands from a remote malicious user:
- Download files
- Perform remote shell
- Retrieve system information
- Update self
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- http://{BLOCKED}t.{BLOCKED}025.{BLOCKED}5.cn/norton/TTip.asp
- http://{BLOCKED}t.{BLOCKED}025.{BLOCKED}5.cn/norton/NfHostInfo.asp
- http://{BLOCKED}t.{BLOCKED}025.{BLOCKED}5.cn/norton/NfStart.asp
- http://{BLOCKED}t.{BLOCKED}025.{BLOCKED}5.cn/norton/Nfile.asp
It posts the following information to its command and control (C&C) server:
- IP configuration
- Network statistics
- Running processes
- Running services
- System information
Download Routine
This backdoor accesses the following websites to download files:
- http://{BLOCKED}t.{BLOCKED}025.{BLOCKED}5.cn/norton/Nfile.asp
It saves the files it downloads using the following names:
- %Temp%\MSMAPI.OCX - also detected as BKDR_NFLOG.AU
(Note: %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp.)
It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.
Other Details
This backdoor requires the existence of the following files to properly run:
- %Temp%\YahooCache.ini
(Note: %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp.)
NOTES:
This backdoor reports system infection by sending the IP address and infection time to the following URL via HTTP post:
- http://{BLOCKED}t.{BLOCKED}025.{BLOCKED}5.cn/norton/NfStart.asp
SOLUTION
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
Remove the malware/grayware file that dropped/downloaded BKDR_NFLOG.AU
- TROJ_MDROP.ZPE
Step 3
Restart in Safe Mode
Step 4
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\SYSTEM\CurrentControlSet\Services
- IPRIP
- IPRIP
Step 5
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_USERS\.DEFAULT\Software\Microsoft\Clock
- HID = {hex values}
- HID = {hex values}
Step 6
Restore these modified registry values
Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths
- From: Directory = "NetworkService's %Temporary Internet Files%\Content.IE5"
To: Directory = %Temporary Internet Files%\Content.IE5
- From: Directory = "NetworkService's %Temporary Internet Files%\Content.IE5"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path1
- From: CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache1"
To: CachePath = %Temporary Internet Files%\Content.IE5\Cache1
- From: CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path2
- From: CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache2"
To: CachePath = %Temporary Internet Files%\Content.IE5\Cache2
- From: CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache2"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path3
- From: CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache3"
To: CachePath = %Temporary Internet Files%\Content.IE5\Cache3
- From: CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache3"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Cache\Paths\path4
- From: CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache4"
To: CachePath = %Temporary Internet Files%\Content.IE5\Cache4
- From: CachePath = "NetworkService's %Temporary Internet Files%\Content.IE5\Cache4"
Step 7
Search and delete this file
- %Temp%\$NtUninstallKB942388$
- %Temp%\NfIpv6.ocx
- %Temp%\YahooCache.ini
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_NFLOG.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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