WORM_UMBALD.AC
TrojanDownloader:Win32/Umbald.A(Microsoft), Backdoor.Win32.Nucleroot(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: Yes
In the wild: Yes
OVERVIEW
Downloaded from the Internet, Dropped by other malware
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 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.
TECHNICAL DETAILS
96,256 bytes
EXE
Yes
07 Aug 2013
Connects to URLs/IPs, Compromises system security, Drops files
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:
- %Windows%\svchost.exe
(Note: %Windows% is the Windows folder, which is usually C:\Windows.)
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Socks Virtual Host = ""%Windows%\svchost.exe""
Other System Modifications
This worm adds the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
bw8legs
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
bw8legs
UID = "{random}"
Propagation
This worm drops the following copy(ies) of itself in all removable drives:
- {drive letter}:\starter.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]
open=starter.exe
Backdoor Routine
This worm executes the following commands from a remote malicious user:
- Uninstall Itself
- Download and Execute Files
- Upload Files
- Install Plugin
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- http://{BLOCKED}x.net/panel/panel/bot.php
- http://{BLOCKED}dlol.com/panel/panel/bot.php
- http://{BLOCKED}kosika.com/panel/panel/bot.php
SOLUTION
9.300
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
Restart in Safe Mode
Step 3
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\SOFTWARE\Microsoft
- bw8legs
- bw8legs
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- Socks Virtual Host = ""%Windows%\svchost.exe""
- Socks Virtual Host = ""%Windows%\svchost.exe""
Step 5
Search and delete AUTORUN.INF files created by WORM_UMBALD.AC that contain these strings
[autorun]
open=starter.exe
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_UMBALD.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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