WORM_DORKBOT.ABM
Worm:Win32/Dorkbot.AM (Microsoft), PWS-Zbot.gen.ary (McAfee), Worm.Win32.Dorkbot (Sunbelt)
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: Yes
In the wild: Yes
OVERVIEW
This worm arrives by connecting affected removable drives to a system. 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 executes commands from a remote malicious user, effectively compromising the affected system.
It deletes the initially executed copy of itself.
TECHNICAL DETAILS
Arrival Details
This worm arrives by connecting affected removable drives to a system.
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 component file(s):
- {removable drive letter}:\snkb0pt\Desktop.ini
- {removable drive letter}:\{folder name}.lnk
- {network drive letter}:\snkb0pt\Desktop.ini
- {network drive letter}:\{folder name}.lnk
It drops the following copies of itself into the affected system:
- %Application Data%\{random}.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 creates the following folders:
- {removable drive letter}:\snkb0pt
- {network drive letter}:\snkb0pt
It adds the following mutexes to ensure that only one of its copies runs at any one time:
- snkb0pt
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}.exe = "%Application Data%\{random}.exe"
Propagation
This worm drops copies of itself in network drives such as the following:
- {network drive letter}:\snkb0pt\snkb0pt.exe
It drops the following copy(ies) of itself in all removable drives:
- {removable drive letter}:\snkb0pt\snkb0pt.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 letter}:\snkb0pt\snkb0pt.exe
;{garbage characters}
{removable or network drive letter}:\snkb0pt\snkb0pt.exe
;{garbage characters}
{removable or network drive letter}:\snkb0pt\snkb0pt.exe
;{garbage characters}
Backdoor Routine
This worm executes the following commands from a remote malicious user:
- Update itself
- Join/Leave an IRC channel
- Download other files
- Perform Slowloris, UDP, and SYN flooding
- Create processes
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- f.{BLOCKED}on.pl
- s.{BLOCKED}b.pl
- {BLOCKED}sbh.org
- {BLOCKED}h.com
- h.{BLOCKED}ws.su
- o.{BLOCKED}adio.su
- {BLOCKED}h.net
- {BLOCKED}sphere.su
- {BLOCKED}obeat.su
- {BLOCKED}us.kei.su
Other Details
This worm deletes the initially executed copy of itself
NOTES:
It downloads files from its C&C servers and saves it as %User Temp%\{random}.exe.
As of this writing, there are no files downloaded upon connecting to the server.
It drops shortcut files pointing to its copy 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.
It connects to any of the following IRC servers:
- {BLOCKED}.{BLOCKED}.71.238:9000
- {BLOCKED}.{BLOCKED}.173.154:9000
- {BLOCKED}.{BLOCKED}.86.198:9000
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.ABM
Step 3
Restart in Safe Mode
Step 4
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}.exe = "%Application Data%\{random}.exe"
- {random}.exe = "%Application Data%\{random}.exe"
Step 5
Search and delete these folders
- {removable drive letter}:\snkb0pt
- {network drive letter}:\snkb0pt
Step 6
Search and delete this file
- {removable drive letter}:\{folder name}.lnk
- {network drive letter}:\{folder name}.lnk
Step 7
Search and delete AUTORUN.INF files created by WORM_DORKBOT.ABM that contain these strings
- ;{garbage characters}
- {removable or network drive letter}:\snkb0pt\snkb0pt.exe
- ;{garbage characters}
- {removable or network drive letter}:\snkb0pt\snkb0pt.exe
- ;{garbage characters}
- {removable or network drive letter}:\snkb0pt\snkb0pt.exe
- ;{garbage characters}
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_DORKBOT.ABM. 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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