It drops a distributed denial of service (DDoS) component that targets primary and secondary DNS name servers of record for multiple South Korean government sites.
To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.
This malware drops several components depending on the operating system of the affected system, whether 32- or 64-bit. It ends with the dropping of a malicious executable that performs the distributed denial of service attack on predetermined IP addresses belonging to South Korea government websites.
This Trojan may be downloaded by other malware/grayware/spyware from remote sites.
It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.
Arrival Details
This Trojan may be downloaded by other malware/grayware/spyware from remote sites.
Installation
This Trojan drops the following file(s)/component(s):
- 64-bit environment:
- %User Temp%\~ER{number}.tmp (64-bit) - detected as HKTL_BYPASS
- %User Temp%\~DR{number}.tmp (64-bit) - detected as TROJ64_DIDKR.C
- 32-bit environment:
- %User Temp%\~DR{number}.tmp (32-bit) - detected as TROJ_DIDKR.C
(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)
Other System Modifications
This Trojan adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{service name of variable 1}Svc\Parameters
ServiceDll = “%System%\ole{variable 1}.dll”
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{service name of variable 1}Svc\Parameters
ServiceMain = “RoutineMain”
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
netsvcs = “{default data}, {service name of variable 1}Svc”
(Note: The default value data of the said registry entry is {default data}.)
Dropping Routine
This Trojan executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.
NOTES:
This malware executes the dropped components in 64-bit environment using the following command line parameters:
- "%User Temp%\~ER{number}.tmp" "%User Temp%\~DR{number}.tmp"
The dropped component %User Temp%\~ER{number}.tmp is capable of elevating administration privileges of ~DR{number}.tmp in default user access control (UAC) settings. The component %User Temp%\~DR{number}.tmp drops the following files:
- 64-bit environment:
- %System%\ole{variable 1}.dll (64-bit) - detected as TROJ64_DIDKR.C
- %User Temp%\~DL{number}.tmp (64-bit) - copy of ole{variable 1}.dll (64-bit)
- 32-bit environment:
- %System%\ole{variable 1}.dll (32-bit) - detected as TROJ_DIDKR.C
- %User Temp%\~DL{number}.tmp (32-bit) - copy of ole{variable 1}.dll (32-bit)
It enumerates all service names that meets the following condition:
- ImagePath = "%SystemRoot%\System32\svchost.exe -k netsvcs"
It then gets {variable 1} from the file name registered in ServiceDll. For example:
ImagePath = "%SystemRoot%\System32\svchost.exe -k netsvcs
ServiceDll = "%System%\shsvcs.dll"
{variable 1} = shsvcs
Thus, the file ole{variable 1}.DLL is dropped as oleshsvcs.DLL in the aforementioned scenario.
The component %System%\ole{variable 1}.dll accesses any of the following sites to receive data:
- http://webmail.{BLOCKED}shost.com/mail/images/ct.jpg
- http://www.{BLOCKED}pic.net/pictures/e02947e8573918c1d887e04e2e0b1570.jpg
It saves the received data to %User Temp%\~MR{number}.TMP. It checks the content of %User Temp%\~MR{number}.tmp if the string BM6W is present. As of this writing, it checks the present date if equal to or greater than June 25 10AM. The date to be compared is present in the received data. It is the 4 bytes of data after BM6W.
The component %System%\ole{variable 1}.DLL drops and executes the following file if the conditions above are met:
- %System%\wuauieop.exe - detected as DDOS_DIDKR.C
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 malware/grayware files dropped/downloaded by TROJ_DIDKR.C
Step 3
Identify and delete files detected as TROJ_DIDKR.C using either the Startup Disk or Recovery Console
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To identify and delete the malware/grayware file:
• On Windows XP and Server 2003 systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Click Start>Run. In the Open input box, type secpol.msc and press Enter.
- In the left panel, double-click Local Policies>Security Options.
- In the right panel, double-click Recovery Console: Allow floppy copy and access to all drives and folders.
- Select Enabled and click OK.
- Insert the Windows Installation CD into the CD drive, then restart your computer.
- When prompted, press any key to boot from the CD.
- On the main menu, type r to go to the Recovery Console.
- Type the number that corresponds to the drive and directory that contains Windows (usually C:\WINDOWS) and press Enter.
- Type the Administrator password and press Enter.
- In the input box, type the following then press Enter:
SET AllowAllPaths = TRUE
del "{malware/grayware path and file name}" - Type exit and press Enter to restart the system normally.
• On Windows Vista and 7 systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Insert your Windows Installation DVD in the DVD drive, then Press the restart button.
- When prompted, press any key to boot from the CD.
- Depending on your Windows Installation DVD, you might be required to select the installation language. Then on the Install Windows window, choose your language, locale, and keyboard layout or input method. Click Next, then click Repair your computer.
- Select Use recovery tools that can help fix problems starting Windows. Select your installation of Windows. Click Next.
- If the Startup Repair window appears, click Cancel, Yes, then Finish.
- In the System Recovery Options window, click Command Prompt.
- In the Command Prompt window, type the following then press Enter:
BootRec.exe /fixmbr
del "{malware/grayware path and file name}" - Type exit and press Enter to close the Command Prompt window.
- Click Restart to restart the system normally.
Step 4
Delete this registry value
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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\{service name of variable 1}Svc\Parameters
- ServiceDll = “%System%\ole{variable 1}.dll”
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\{service name of variable 1}Svc\Parameters
- ServiceMain = “RoutineMain”
To delete the registry value this malware created:
- Open Registry Editor. To do this, click Start>Run, type regedit in the text box provided, then press Enter.
- In the left panel of the Registry Editor window, double-click the following:
HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>Services>{service name of variable 1}Svc>Parameters - In the right panel, locate and delete the entry:
ServiceDll = “%System%\ole{variable 1}.dll” - In the left panel of the Registry Editor window, double-click the following:
HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>Services>{service name of variable 1}vc>Parameters - In the right panel, locate and delete the entry:
ServiceMain = “RoutineMain” - Close Registry Editor.
Step 5
Restore this modified registry value
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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 = “{default data}, {service name of variable 1}Svc”
To: netsvcs = "{default data}"
To restore the registry value this malware/grayware modified:
- Open Registry Editor. Click Start>Run, type REGEDIT in the text box provided, and then press Enter.
- In the left panel, double-click the following:
HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>SvcHost - In the right panel, locate the registry value:
netsvcs = “{default data}, {service name of variable 1}Svc” - Right-click on the value name and choose Modify. Change the value data of this entry to:
netsvcs = "{default data}" - Close Registry Editor.
Step 6
Search and delete this file
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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.
- %User Temp%\~MR{number}.tmp
To delete the grayware/spyware file:
- Right-click Start then click Search... or Find..., depending on the version of Windows you are running.
- In the Named input box, type:
- %User Temp%\~MR{number}.tmp
- In the Look In drop-down list, select My Computer, then press Enter.
- Once located, select the file then press SHIFT+DELETE.
Step 7
Scan your computer with your Trend Micro product to delete files detected as TROJ_DIDKR.C. 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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