WORM_DORKBOT.MC
Worm:Win32/Dorkbot.A (Microsoft), W32.IRCBot.NG (Norton), W32/IRCbot.gen.a (NAI), W32/Dorkbot-FH (Sophos), Worm.Win32.Dorkbot (Sunbelt), W32/Ruskill.B!tr.bdr (Fortinet), Backdoor.Win32.Ruskill (Ikarus)
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It executes then deletes itself afterward.
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
TECHNICAL DETAILS
Arrival Details
This worm 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 worm drops the following copies of itself into the affected system and executes them:
- %Application Data%\{RANDOM_FILE_NAME}.exe
(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)
It drops the following files:
- %Application Data%\B.exe
- %User Temp%\libcurl-4.dll
- %User Temp%\minerd.exe
- %User Temp%\pthreadGC2.dll
- %Windows%\INETINFO.exe
- %System%\inf\svchost.exe
(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.. %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.. %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.)
It creates the following folders:
- %Windows%\system32\inf
(Note: %Windows% is the Windows folder, which is usually C:\Windows.)
It executes then deletes itself afterward.
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{RANDOM_FILE_NAME} = "%Application Data%\{RANDOM_FILE_NAME}.exe"
Other System Modifications
This worm adds the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_EVENTCHK
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\eventchk
It creates the following registry entry(ies) to bypass Windows Firewall:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\inf\svchost.exe = "%System%\inf\svchost.exe:*:Enabled:@xpsp2res.dll,-22001"
Propagation
This worm creates the following folders in all removable drives:
- {DRIVE_LETTER}:\RECYCLER
It drops the following copy(ies) of itself in all removable drives:
- {DRIVE_LETTER}:\RECYCLER\{RANDOM_FILE_NAME}.exe
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
The said .INF file contains the following strings:
[AutoRun]
;{GARBAGE_CHARACTERS}
shellexecute=RECYCLER\{RANDOM_FILE_NAME}.exe
;{GARBAGE_CHARACTERS}
icon=shell32.dll,7
;{GARBAGE_CHARACTERS}
shell\open\command=RECYCLER\{RANDOM_FILE_NAME}.exe
;{GARBAGE_CHARACTERS}
action=Open folder to view files
;{GARBAGE_CHARACTERS}
shell\explore\command=RECYCLER\{RANDOM_FILE_NAME}.exe
;{GARBAGE_CHARACTERS}
useautoplay=1
Other Details
This worm connects to the following URL(s) to get the affected system's IP address:
- http://api.wipmania.com
It connects to the following possibly malicious URL:
- http://{BLOCKED}ivb.googlepages.com/NWB.txt
- {BLOCKED}5.com
NOTES:
It drops shortcut files pointing to the copy of itself in removable drives. These dropped .LNK files use the names of the folders located on the said drives for their file names. It then sets the attributes of the original folders to Hidden to trick the user into clicking the .LNK files.
SOLUTION
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
Scan your computer with your Trend Micro product and note files detected as WORM_DORKBOT.MC
Step 3
Restart in Safe Mode
Step 4
Search and delete these files
- %Application Data%\{RANDOM_FILE_NAME}.exe
- %Application Data%\B.exe
- %User Temp%\libcurl-4.dll
- %User Temp%\minerd.exe
- %User Temp%\pthreadGC2.dll
- %Windows%\INETINFO.exe
Step 5
Search and delete these folders
- %Windows%\system32\inf
- {DRIVE_LETTER}:\RECYCLER
Step 6
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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- {RANDOM_FILE_NAME} = "%Application Data%\{RANDOM_FILE_NAME}.exe"
- {RANDOM_FILE_NAME} = "%Application Data%\{RANDOM_FILE_NAME}.exe"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- %System%\inf\svchost.exe = "%System%\inf\svchost.exe:*:Enabled:@xpsp2res.dll,-22001"
- %System%\inf\svchost.exe = "%System%\inf\svchost.exe:*:Enabled:@xpsp2res.dll,-22001"
Step 7
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\Enum\Root
- LEGACY_EVENTCHK
- LEGACY_EVENTCHK
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- eventchk
- eventchk
Step 8
Search and delete AUTORUN.INF files created by WORM_DORKBOT.MC that contain these strings
;{GARBAGE_CHARACTERS}
shellexecute=RECYCLER\{RANDOM_FILE_NAME}.exe
;{GARBAGE_CHARACTERS}
icon=shell32.dll,7
;{GARBAGE_CHARACTERS}
shell\open\command=RECYCLER\{RANDOM_FILE_NAME}.exe
;{GARBAGE_CHARACTERS}
action=Open folder to view files
;{GARBAGE_CHARACTERS}
shell\explore\command=RECYCLER\{RANDOM_FILE_NAME}.exe
;{GARBAGE_CHARACTERS}
useautoplay=1
Step 9
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_DORKBOT.MC. 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.
Did this description help? Tell us how we did.