BKDR_ZEGOST.RP
Backdoor:Win32/Zegost.Z (Microsoft); Trojan.Win32.Generic!BT (Sunbelt)
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This backdoor 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
1,493,651 bytes
EXE
Yes
27 Aug 2012
Arrival Details
This backdoor 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 backdoor drops the following copies of itself into the affected system:
- %User Temp%\~__UNINST.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.)
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{309ED2D7-40E7-46f1-881C-79D3BC5CF780}
stubpath = "%System%\innfvgrkz.exe"
It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSEt\
Services\PCRatStact
Other System Modifications
This backdoor deletes the following files:
- %User Temp%\~pmThis.tmp
- %Windows%\fonts\msgothic.ttf
- %Windows%\fonts\msuigoth.ttf
- %Windows%\fonts\MSMINCHO.TTF
- %Windows%\fonts\Gulim.ttf
- %Windows%\fonts\Gulimche.ttf
- %Windows%\fonts\Dotum.ttf
- %Windows%\fonts\Batang.ttf
- %Windows%\fonts\Gungsuh.ttf
- %Windows%\fonts\Simsun.ttf
- %Windows%\fonts\nsimsun.ttf
- %Windows%\fonts\MingLiU.ttf
- %Windows%\fonts\pmingliu.ttf
- %System%\SET2.tmp
- %System%\kbd101b.dll
- %System%\SET4.tmp
- %System%\kbd101c.dll
- %System%\SET6.tmp
- %System%\kbd103.dll
- %System%\SET8.tmp
- %System%\kbd106.dll
- %System%\SETA.tmp
- %System%\kbdjpn.dll
- %System%\SETC.tmp
- %System%\kbdkor.dll
(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.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %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 adds the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{309ED2D7-40E7-46f1-881C-79D3BC5CF780}
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\PCRatStact
Type = "12"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
Enable = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
Size = "a"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
InitHits = "64"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International\CpMRU
Factor = "14"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International
W2KLpk = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\International
W2KLpk = "0"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\SFC
ProgramFilesDir = "%Program Files%"
(Note: The default value data of the said registry entry is %Program Files%.)
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\SFC
CommonFilesDir = "%Program Files%\Common Files"
(Note: The default value data of the said registry entry is %Program Files%\Common Files.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DirectDraw\MostRecentApplication
Name = "iexplore.exe"
(Note: The default value data of the said registry entry is iexplore.exe.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DirectDraw\MostRecentApplication
ID = "4117b81"
(Note: The default value data of the said registry entry is 41107b81.)
It deletes the following registry keys:
HKEY_CURRENT_USER\Software\Microsoft\
Active Setup\Installed Components\{309ED2D7-40E7-46f1-881C-79D3BC5CF780}
Dropping Routine
This backdoor drops the following files:
- %User Temp%\server.exe
- %User Temp%\ÀÌÄÚ³ë¹Ì¯°³±¤Å¬.exe
- %System%\innfvgrkz.exe
- %User Temp%\35781_res.tmp
- %System%\SET1.tmp
- %System%\SET3.tmp
- %System%\SET5.tmp
- %System%\SET7.tmp
- %System%\SET9.tmp
- %System%\SETB.tmp
- %User Temp%\~pmThis.tmp
- %System%\SET2.tmp
- %System%\SET4.tmp
- %System%\SET6.tmp
- %System%\SET8.tmp
- %System%\SETA.tmp
- %System%\SETC.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.. %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.)
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
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\SYSTEM\CurrentControlSEt\Services
- PCRatStact
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
- {309ED2D7-40E7-46f1-881C-79D3BC5CF780}
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International
- CpMRU
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\Microsoft\Active Setup\Installed Components\{309ED2D7-40E7-46f1-881C-79D3BC5CF780}
- stubpath = "%System%\innfvgrkz.exe"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\PCRatStact
- Type = "12"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International\CpMRU
- Enable = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International\CpMRU
- Size = "a"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International\CpMRU
- InitHits = "64"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International\CpMRU
- Factor = "14"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International
- W2KLpk = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\International
- W2KLpk = "0"
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\ControlSet001\Control\Session Manager\SFC
- From: ProgramFilesDir = "%Program Files%"
To: ProgramFilesDir = ""%Program Files%""
- From: ProgramFilesDir = "%Program Files%"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\SFC
- From: CommonFilesDir = "%Program Files%\Common Files"
To: CommonFilesDir = ""%Program Files%\Common Files""
- From: CommonFilesDir = "%Program Files%\Common Files"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectDraw\MostRecentApplication
- From: Name = "iexplore.exe"
To: Name = ""iexplore.exe""
- From: Name = "iexplore.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectDraw\MostRecentApplication
- From: ID = "4117b81"
To: ID = ""41107b81""
- From: ID = "4117b81"
Step 6
Search and delete these files
- %User Temp%\server.exe
- %User Temp%\ÀÌÄÚ³ë¹Ì¯°³±¤Å¬.exe
- %System%\innfvgrkz.exe
- %User Temp%\35781_res.tmp
- %System%\SET1.tmp
- %System%\SET3.tmp
- %System%\SET5.tmp
- %System%\SET7.tmp
- %System%\SET9.tmp
- %System%\SETB.tmp
- %User Temp%\~pmThis.tmp
- %System%\SET2.tmp
- %System%\SET4.tmp
- %System%\SET6.tmp
- %System%\SET8.tmp
- %System%\SETA.tmp
- %System%\SETC.tmp
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ZEGOST.RP. 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 this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.
- %User Temp%\~pmThis.tmp
- %Windows%\fonts\msgothic.ttf
- %Windows%\fonts\msuigoth.ttf
- %Windows%\fonts\MSMINCHO.TTF
- %Windows%\fonts\Gulim.ttf
- %Windows%\fonts\Gulimche.ttf
- %Windows%\fonts\Dotum.ttf
- %Windows%\fonts\Batang.ttf
- %Windows%\fonts\Gungsuh.ttf
- %Windows%\fonts\Simsun.ttf
- %Windows%\fonts\nsimsun.ttf
- %Windows%\fonts\MingLiU.ttf
- %Windows%\fonts\pmingliu.ttf
- %System%\SET2.tmp
- %System%\kbd101b.dll
- %System%\SET4.tmp
- %System%\kbd101c.dll
- %System%\SET6.tmp
- %System%\kbd103.dll
- %System%\SET8.tmp
- %System%\kbd106.dll
- %System%\SETA.tmp
- %System%\kbdjpn.dll
- %System%\SETC.tmp
- %System%\kbdkor.dll
Step 9
Restore these deleted registry keys/values from backup
*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.
- In HKEY_CURRENT_USER\Software\Microsoft\Active Setup\Installed Components
- {309ED2D7-40E7-46f1-881C-79D3BC5CF780}
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