TROJ_ENCPDF.A
Troj/EncPdf-A (Sophos); W32/EncPdf.A!tr (Fortinet)
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Trojan
Destructiveness: No
Encrypted: No
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
685,568 bytes
EXE
Yes
08 Apr 2011
Modifies HOSTS file, Drops files
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%\mstap32.exe - also detected as TROJ_ENCPDF.A
- %System%\htdns.dll - non-malicious file
- %User Temp%\GeoIP.dat - non-malicious file
- %Windows%\pdoor.exe - non-malicious file
(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 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.)
Autostart Technique
This Trojan modifies the following registry entries to ensure it automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = %System%\userinit.exe,%System%\mstap32.exe
(Note: The default value data of the said registry entry is %System%\userinit.exe,.)
Other System Modifications
This Trojan adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
EnableLUA = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0002
EnableForRas = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0002
EnableForRouting = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0002
EnableForOutboundRouting = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0003
EnableForRas = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0003
EnableForRouting = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0003
EnableForOutboundRouting = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0004
EnableForRas = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0004
EnableForRouting = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0004
EnableForOutboundRouting = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0005
EnableForRas = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0005
EnableForRouting = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\
0005
EnableForOutboundRouting = 0
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\RasMan\Parameters
IpOutLowWatermark = 1
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\RasMan\Parameters
IpOutHighWatermark = 5
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\RasMan\Parameters
NbfOutLowWatermark = 1
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\RasMan\Parameters
NbfOutHighWatermark = 5
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\RasMan\Parameters
NbfInLowWatermark = 1
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\RasMan\Parameters
NbfInHighWatermark = 5
It adds the following registry keys as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\BAP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\PPP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASBACP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASCCP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASEAP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASIPCP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASIPHLP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASMAN
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASPAP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASQEC
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASSPAP
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\RASTAPI
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Eventlog\Application\
Microsoft H.323 Telephony Service Provider
HOSTS File Modification
This Trojan adds the following strings to the Windows HOSTS file:
- 69.90.81.66 {username}
SOLUTION
8.900
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 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\Windows\CurrentVersion\policies\system
- EnableLUA = 0
- EnableLUA = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0002
- EnableForRas = 0
- EnableForRas = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0002
- EnableForRouting = 0
- EnableForRouting = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0002
- EnableForOutboundRouting = 0
- EnableForOutboundRouting = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0003
- EnableForRas = 0
- EnableForRas = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0003
- EnableForRouting = 0
- EnableForRouting = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0003
- EnableForOutboundRouting = 0
- EnableForOutboundRouting = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0004
- EnableForRas = 0
- EnableForRas = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0004
- EnableForRouting = 0
- EnableForRouting = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0004
- EnableForOutboundRouting = 0
- EnableForOutboundRouting = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0005
- EnableForRas = 0
- EnableForRas = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0005
- EnableForRouting = 0
- EnableForRouting = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\0005
- EnableForOutboundRouting = 0
- EnableForOutboundRouting = 0
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RasMan\Parameters
- IpOutLowWatermark = 1
- IpOutLowWatermark = 1
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RasMan\Parameters
- IpOutHighWatermark = 5
- IpOutHighWatermark = 5
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RasMan\Parameters
- NbfOutLowWatermark = 1
- NbfOutLowWatermark = 1
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RasMan\Parameters
- NbfOutHighWatermark = 5
- NbfOutHighWatermark = 5
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RasMan\Parameters
- NbfInLowWatermark = 1
- NbfInLowWatermark = 1
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RasMan\Parameters
- NbfInHighWatermark = 5
- NbfInHighWatermark = 5
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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- BAP
- BAP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- PPP
- PPP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASBACP
- RASBACP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASCCP
- RASCCP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASEAP
- RASEAP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASIPCP
- RASIPCP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASIPHLP
- RASIPHLP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASMAN
- RASMAN
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASPAP
- RASPAP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASQEC
- RASQEC
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASSPAP
- RASSPAP
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Tracing
- RASTAPI
- RASTAPI
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Eventlog\Application
- Microsoft H.323 Telephony Service Provider
- Microsoft H.323 Telephony Service Provider
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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Userinit = %System%\userinit.exe,%System%\mstap32.exe
To: %System%\userinit.exe,
- From: Userinit = %System%\userinit.exe,%System%\mstap32.exe
Step 6
Remove these strings added by the malware/grayware/spyware in the HOSTS file
- 69.90.81.66 {username}
Step 7
Search and delete this file
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_ENCPDF.A. 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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