Worm:Win32/Brontok.AO@mm is a member of
Win32/Brontok - a family of mass-mailing email worms. The worm spreads by sending a copy of itself as an email attachment to email addresses that it gathers from files on the infected computer. It can also copy itself to USB and pen drives.
Win32/Brontok can disable antivirus and security software, immediately terminate certain applications, and cause Windows to restart when certain applications run. The worm may also conduct denial of service (DoS) attacks against certain websites.
Installation
When executed, Worm:Win32/Brontok.AO@mm copies itself to the following locations:
- %windir%\sembako-cjzjlmi.exe
- %windir%\shellnew\bbm-xqtlmijc.exe
- <system folder>\administrator's setting.scr
- <system folder>\cmd-bro-mlx.exe
- <system folder>\dxblbm.exe
- c:\documents and settings\administrator\local settings\application data\br7911on.exe
- c:\documents and settings\administrator\local settings\application data\csrss.exe
- c:\documents and settings\administrator\local settings\application data\inetinfo.exe
- c:\documents and settings\administrator\local settings\application data\lsass.exe
- c:\documents and settings\administrator\local settings\application data\services.exe
- c:\documents and settings\administrator\local settings\application data\smss.exe
- c:\documents and settings\administrator\local settings\application data\svchost.exe
- c:\documents and settings\administrator\local settings\application data\winlogon.exe
- c:\documents and settings\administrator\start menu\programs\startup\empty.pif
- c:\documents and settings\administrator\templates\14004-nendangbro.com
Note: <system folder> refers to a variable location that is determined by the malware by querying the Operating System. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP, Vista, and 7 is C:\Windows\System32.
The malware modifies the following registry entries to ensure that its copy executes at each Windows start:
Adds value: "Tok-Cirrhatus-3444"
With data: "c:\documents and settings\administrator\local settings\application data\br7911on.exe"
To subkey: HKCU\Software\Microsoft\windows\currentversion\run
Adds value: "Shell"
With data: "explorer.exe "c:\windows\sembako-cjzjlmi.exe""
To subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
The malware creates the following files on an affected computer:
-
<system folder>\sistem.sys
-
c:\autoexec.bat
-
c:\documents and settings\administrator\local settings\application data\bronmesmalware.dat.ini
-
c:\documents and settings\administrator\local settings\application data\bronmessmss.ini
-
c:\documents and settings\administrator\local settings\application data\bronmeswinlogon.ini
Payload
Modifies system settings
Worm:Win32/Brontok.AO@mm removes the Folder Options item from all Explorer menus and the Control Panel by making the following registry modification:
Adds value:
"NoFolderOptions" With data:
"1" To subkey:
HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\ExplorerNote: Removing access to these options may hinder the affected user's ability to detect and remove malware.
This malware description was produced and published using our automated analysis system's examination of file SHA1 b852bac5435441520b0630860bd17cd3aec04f9b.
