ALIASES:

Backdoor:Win32/Agent.EK (Microsoft); BackDoor-CMA (McAfee); W32.SillyP2P (Symantec); Backdoor.Win32.Agent.ek (Kaspersky); BehavesLike.Win32.Malware.ssc (mx-v) (Sunbelt); Trojan horse BackDoor.Agent.4.AF (AVG)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • 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.

It disables Task Manager, Registry Editor, and Folder Options.

  TECHNICAL DETAILS

File Size: 497,116 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 08 May 2013

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:

  • %Program Files%\Adobe\Reader 10.0\Reader\_Reader32.exe
  • %System%\_textpad.exe
  • %System%\AC3D21A09E72
  • %System%\system.bin

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).. %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
®Windows Update = "svchosts.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
®Windows Update = "svchosts.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\TSKNF501.SYS

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\KmxFile

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\KmxIds

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\KmxAgent

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\KmxBiG

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\KmxCfg

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\KmxFw

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\KmxNdis

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\KmxSbx

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID
LocalThread = "false"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\TSKNF501.SYS
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\KmxFile
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\KmxIds
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\KmxAgent
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\KmxBiG
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\KmxCfg
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\KmxFw
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\KmxNdis
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\KmxSbx
Start = "4"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Telephony\
Providers
ProviderID6 = "7"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Telephony\
Providers
ProviderFileName6 = "avmtapi.tsp"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Telephony\
Providers
AllProviders = "true"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID
ThreadingModel = "false"

HKEY_LOCAL_MACHINE\SYSTEM
ThreadingModel = "false"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
®Windows Update = "svchosts.exe"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Telephony\
Providers
NumProviders = "7"

(Note: The default value data of the said registry entry is 6.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Telephony\
Providers
NextProviderID = "8"

(Note: The default value data of the said registry entry is 7.)

It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
®Windows Update = "svchosts.exe"

Dropping Routine

This backdoor drops the following files:

  • %Program Files%\Adobe\Reader 10.0\Reader\_Reader32.exe
  • %System%\_textpad.exe
  • %System%\ntuser.dat
  • %System%\kernell32.dll
  • %System%\avmtapi.tsp
  • %System%\system.dll
  • %System%\svchosts.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).. %System% is the Windows system folder, which is usually C:\Windows\System32.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.300

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

Restart in Safe Mode

[ Learn More ]

Step 3

Enable Registry Editor, Task Manager, and Folder options

[ Learn More ]
By doing this step, you also enable other applications/programs disabled by this malware/grayware/spyware.

Step 4

Delete this registry key

[ Learn More ]

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
    • TSKNF501.SYS
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • KmxFile
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • KmxIds
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • KmxAgent
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • KmxBiG
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • KmxCfg
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • KmxFw
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • KmxNdis
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • KmxSbx
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Run
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Run

Step 5

Delete this registry value

[ Learn More ]

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\Run
    • ®Windows Update = "svchosts.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • ®Windows Update = "svchosts.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
    • LocalThread = "false"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\TSKNF501.SYS
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\KmxFile
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\KmxIds
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\KmxAgent
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\KmxBiG
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\KmxCfg
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\KmxFw
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\KmxNdis
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\KmxSbx
    • Start = "4"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Telephony\Providers
    • ProviderID6 = "7"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Telephony\Providers
    • ProviderFileName6 = "avmtapi.tsp"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Telephony\Providers
    • AllProviders = "true"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
    • ThreadingModel = "false"
  • In HKEY_LOCAL_MACHINE\SYSTEM
    • ThreadingModel = "false"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • ®Windows Update = "svchosts.exe"

Step 6

Restore these modified registry values

[ Learn More ]

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\Telephony\Providers
    • From: NumProviders = "7"
      To: NumProviders = ""6""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Telephony\Providers
    • From: NextProviderID = "8"
      To: NextProviderID = ""7""

Step 7

Search and delete these components

[ Learn More ]
There may be some components that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Program Files%\Adobe\Reader 10.0\Reader\_Reader32.exe
  • %System%\_textpad.exe
  • %System%\ntuser.dat
  • %System%\kernell32.dll
  • %System%\avmtapi.tsp
  • %System%\system.dll
  • %System%\svchosts.exe

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_AGENT.AYKK. 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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