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TROJ_DELF_0000056.TOMA

October 12, 2012
 ALIASES:

Backdoor:Win32/Delf.IS (Microsoft); Generic BackDoor!dpr (McAfee); Backdoor.Win32.Shark.ag (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Backdoor.Generic.138224 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • 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.

  TECHNICAL DETAILS

File Size:

389,636 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Oct 2011

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 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\windows xp\Parameters

Other System Modifications

This Trojan deletes the following files:

  • {malware path and file name}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\windows xp\Parameters
ServiceDll = "%System%\dgrat.dll"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\windows xp
Description = "windows xp"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\windows xp
LinkName = "DG RAT"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
netsvcs = ""6to4,AppMgmt,AudioSrv,Browser,CryptSvc,DMServer,DHCP,ERSvc,EventSystem,FastUserSwitchingCompatibility,HidServ,Ias,Iprip,Irmon,LanmanServer,LanmanWorkstation,Messenger,Netman,Nla,Ntmssvc,NWCWorkstation,Nwsapagent,Rasauto,Rasman,Remoteaccess,Schedule,Seclogon,SENS,Sharedaccess,SRService,Tapisrv,Themes,TrkWks,W32Time,WZCSVC,Wmi,WmdmPmSp,winmgmt,wscsvc,xmlprov,BITS,wuauserv,ShellHWDetection,helpsvc,WmdmPmSN,windows xp""

(Note: The default value data of the said registry entry is 6to4.)

Dropping Routine

This Trojan drops the following files:

  • %System%\dgrat.dll

(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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

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

[ Learn More ]

Step 3

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\windows xp
    • Parameters

Step 4

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\SYSTEM\ControlSet001\Services\windows xp\Parameters
    • ServiceDll="%System%\dgrat.dll"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\windows xp
    • Description="windows xp"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\windows xp
    • LinkName="DG RAT"

Step 5

Restore this modified 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 NT\CurrentVersion\SvcHost
    • From: netsvcs=""6to4,AppMgmt,AudioSrv,Browser,CryptSvc,DMServer,DHCP,ERSvc,EventSystem,FastUserSwitchingCompatibility,HidServ,Ias,Iprip,Irmon,LanmanServer,LanmanWorkstation,Messenger,Netman,Nla,Ntmssvc,NWCWorkstation,Nwsapagent,Rasauto,Rasman,Remoteaccess,Schedule,Seclogon,SENS,Sharedaccess,SRService,Tapisrv,Themes,TrkWks,W32Time,WZCSVC,Wmi,WmdmPmSp,winmgmt,wscsvc,xmlprov,BITS,wuauserv,ShellHWDetection,helpsvc,WmdmPmSN,windows xp""
      To: netsvcs=6to4

Step 6

Search and delete this file

[ Learn More ]
There may be some component files 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. %System%\dgrat.dll

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DELF_0000056.TOMA. 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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