WORM_DORKBOT.LS
Trojan:Win32/Ircbrute (Microsoft), Trojan.Win32.Ircbrute (Vipre), W32/Nomkesh.C (Fortinet), Trojan.Win32.Ircbrute (Ikarus), Win32/Nomkesh.C worm (ESET),
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 via removable drives. It arrives by accessing affected shared networks. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
It deletes the initially executed copy of itself.
TECHNICAL DETAILS
204,288 bytes
EXE
No
01 May 2013
Arrival Details
This worm arrives via removable drives.
It arrives by accessing affected shared networks.
It 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.)
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}.exe = "%Application Data%\{random file name}.exe"
Propagation
This worm creates the following folders in all removable drives:
- {removable drive}:\snkb0ptz
It drops copies of itself in network drives such as the following:
- {network drive}:\snkb0ptz\snkb0ptz.exe
It drops the following copy(ies) of itself in all removable drives:
- {removable drive}:\snkb0ptz\snkb0ptz.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:
;{garbage characters}
{removable or network drive}:\snkb0ptz\snkb0ptz.exe
;{garbage characters}
{removable or network drive}:\snkb0ptz\snkb0ptz.exe
;{garbage characters}
{removable or network drive}:\snkb0ptz\snkb0ptz.exe
;{garbage characters}
Other Details
This worm connects to the following possibly malicious URL:
- {BLOCKED}.{BLOCKED}on.pl
- {BLOCKED}.{BLOCKED}b.pl
- {BLOCKED}h.org
It deletes the initially executed copy of itself
NOTES:
It drops shortcut files pointing to the copy of itself in removable and network 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
9.300
9.890.03
01 May 2013
9.891.00
02 May 2013
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.LS
Step 3
Restart in Safe Mode
Step 4
Delete the registry entry with an unknown data 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.
- HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
Step 5
Search and delete these files
- {removable or network drive}:\snkb0ptz
Step 6
Search and delete AUTORUN.INF files created by WORM_DORKBOT.LS that contain these strings
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_DORKBOT.LS. 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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