WORM_AMBLER.AC
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted: No
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 registers itself as a Browser Helper Object (BHO) to ensure its automatic execution every time Internet Explorer is run. It does this by creating registry keys/entries.
It drops copies of itself into all the removable drives connected to an affected system. 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 component file(s):
- %System%\kmsvc32.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.)
It drops the following non-malicious files:
- %System%\inform.dat
- %System%\wh
(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.)
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_CLASSES_ROOT\CLSID\{684EE1DB-CD52-4ca9-9CCF-93D5F6B419BA}\
InprocServer32
(Default) = "kmsvc32.dll"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{0EA88F0F-B698-4ab1-8DBC-EBE2CD00927F}
StubPath = "rundll32 kmsvc32.dll,InitO"
It registers itself as a Browser Helper Object (BHO) to ensure its automatic execution every time Internet Explorer is run. It does this by creating the following registry key(s)/entry(ies):
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{684EE1DB-CD52-4ca9-9CCF-93D5F6B419BA}
Other System Modifications
This worm adds the following registry entries as part of its installation routine:
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Enable Browser Extensions = "yes"
HKEY_LOCAL_MACHINE\SOFTWARE\Google
MJ1 = "hex:63,77,60,20,"
HKEY_LOCAL_MACHINE\SOFTWARE\Google
MJ2 = "hex:63,77,60,23,"
HKEY_LOCAL_MACHINE\SOFTWARE\Google
MJ3 = "hex:63,77,60,22,"
HKEY_LOCAL_MACHINE\SOFTWARE\Google
Add = "hex:79,7d,64,70,60,76,64,70,61,7e,3c,70,7e,7f,3c,70,61,66,62,"
HKEY_LOCAL_MACHINE\SOFTWARE\Google
LN = "@FX]HOGG"
HKEY_LOCAL_MACHINE\SOFTWARE\Google
COD = "l!/#RR&SU:TS"%:#tv.:.TTQ:.$S"Q!U#&.UVj"
Propagation
This worm drops copies of itself into all the removable drives connected to an affected system.
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
The said .INF file contains the following strings:
[autorun]
open=RECYCLER\recycld.exe
icon=%SystemRoot%\system32\SHELL32.dll,4
action=Open folder to view files
shell\open=Open
shell\open\command=RECYCLER\recycld.exe
shell\open\default=1
SOLUTION
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Restart in Safe Mode
Step 3
Delete this registry value
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- Enable Browser Extensions = "yes"
- Enable Browser Extensions = "yes"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Google
- MJ1 = "hex:63,77,60,20,"
- MJ1 = "hex:63,77,60,20,"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Google
- MJ2 = "hex:63,77,60,23,"
- MJ2 = "hex:63,77,60,23,"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Google
- MJ3 = "hex:63,77,60,22,"
- MJ3 = "hex:63,77,60,22,"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Google
- Add = "hex:79,7d,64,70,60,76,64,70,61,7e,3c,70,7e,7f,3c,70,61,66,62,"
- Add = "hex:79,7d,64,70,60,76,64,70,61,7e,3c,70,7e,7f,3c,70,61,66,62,"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Google
- LN = "@FX]HOGG"
- LN = "@FX]HOGG"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Google
- COD = "l!/#RR&SU:TS"%:#tv.:.TTQ:.$S"Q!U#&.UVj"
- COD = "l!/#RR&SU:TS"%:#tv.:.TTQ:.$S"Q!U#&.UVj"
Step 4
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_CLASSES_ROOT\CLSID
- {684EE1DB-CD52-4ca9-9CCF-93D5F6B419BA}
- {684EE1DB-CD52-4ca9-9CCF-93D5F6B419BA}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
- {0EA88F0F-B698-4ab1-8DBC-EBE2CD00927F}
- {0EA88F0F-B698-4ab1-8DBC-EBE2CD00927F}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects
- {684EE1DB-CD52-4ca9-9CCF-93D5F6B419BA}
- {684EE1DB-CD52-4ca9-9CCF-93D5F6B419BA}
Step 5
Search and delete AUTORUN.INF files created by WORM_AMBLER.AC that contain these strings
Step 6
Search and delete these files
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_AMBLER.AC. 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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