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Worm:Win32/Brontok.A@mm

First posted on 23 August 2011.
Source: SecurityHome

Aliases :

Worm:Win32/Brontok.A@mm is also known as W32/Rontokbro@MM!h (McAfee), Sus/UnkPacker (Sophos), W32.Rontokbro.D@mm (Symantec).

Explanation :

Worm:Win32/Brontok.A@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.
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Worm:Win32/Brontok.A@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.A@mm copies itself to the following locations:

• %windir%\eksplorasi.pif
• %windir%\shellnew\bronstab.exe
• <system folder>\administrator's setting.scr
• 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\winlogon.exe
• c:\documents and settings\administrator\start menu\programs\startup\empty.pif
• c:\documents and settings\administrator\templates\wowtumpeh.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: "Bron-Spizaetus"
With data: "c:\windows\shellnew\bronstab.exe"
To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Adds value: "Tok-Cirrhatus"
With data: "c:\documents and settings\administrator\local settings\application data\smss.exe"
To subkey: HKCU\Software\Microsoft\windows\currentversion\run
Adds value: "Shell"
With data: "explorer.exe "c:\windows\eksplorasi.pif""
To subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
The malware creates the following files on an affected computer:

• c:\autoexec.bat

Payload Modifies system settings Worm:Win32/Brontok.A@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\Explorer

Note: Removing access to these options may hinder the affected user's ability to detect and remove malware.
Contacts remote hostThe malware may contact a remote host at www.geocities.com using port 80. Commonly, malware may contact a remote host for the following purposes:

• To report a new infection to its author
• To receive configuration or other data
• To download and execute arbitrary files (including updates or additional malware)
• To receive instruction from a remote attacker
• To upload data taken from the affected computer

This malware description was produced and published using our automated analysis system's examination of file SHA1 4c5b6cdb36c81f10ccd34e11f14be70f22718222.

Last update 23 August 2011

 

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