W32.Reztrict@mm

Once executed, the worm displays the following message, if the worm already exists on the compromised computer:
No abras el virus 2 veces pelotud@!!

The worm then drops and executes the following VB Script
%UserProfile%\Local Settings\Temp\VIRUS v2.0.vbs

It then downloads the following file:
[http://]diexe.t35.com/viru[REMOVED]

The worm then saves this as the following file and executes it:
%Windir%\addins\svchost.exe

The worm creates the following registry entry so that it runs when Windows starts:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\"svchost" = "%Windir%\addins\svchost.exe"

The worm modifies the following registry entries, which disables the Find, Run, Shut Down, and Log Off options in the Start menu:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"NoFind" = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"NoRun" = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"NoClose" = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"StartMenuLogOff" = "1"

It also modifies the following registry entries, which hide desktop icons, the system clock, disables access to the Control Panel, and changes the Internet Explorer home page:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\"" = "(valor no establecido)"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"NoDesktop" = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"HideClock" = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"NoControlPanel" = "1"
HKEY_CURRENT_USER\Software\Policies\Microsoft\"Homepage" = "1"
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main\"Start Page" = "[http://]prostitutas.com"

The worm enumerates the Windows Messenger contacts and stores them in the following file:
%Windir%\mis contactos.txt

It then reads email addresses from the following registry subkey:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\UnreadMail

It then stores the email addresses in the following file:
%Windir%\mis contactos.txt

It uses the following connection information:
smtp server: mx-adinet.adinet.com.uy
username: marcedeo[REMOVED]et.com.uy
password: di[REMOVED]1

It then sends the following email to email addresses gathered from the registry subkey:
From: Marcel[REMOVED]a <marcedeo[REMOVED]t.com.uy>
To: [GATHERED EMAIL ADDRESS]
Subject: COmo andan??? tanto tiempo che!!
Message body: Y che como estan!! tanto tiempo!! el ot[REMOVED]s todos los gurises!

It may also send the same email message to contacts gathered from Windows Live Messenger with the following characteristics:
From: [WINDOWS LIVE MESSENGER USERNAME]
To: [GATHERED WINDOWS LIVE MESSENGER CONTACT EMAIL ADDRESS]
Subject: COmo andan??? tanto tiempo che!!
Message body: Y che como estan!! tanto tiempo!! el ot[REMOVED]s todos los gurises! [WINDOWS LIVE MESSENGER USERNAME]

It also sends an email to the attacker containing all the harvested contact information:
From: [WINDOWS LIVE MESSENGER USERNAME] <marcedeo[REMOVED]t.com.uy>
To: marcede[REMOVED]ail.com
Subject: MSN TQM!!! como estas?
Message body: MSN cagado: Andres Andrade se la come!!!
Attachment: %Windir%\mis contactos.txt

It then ends the following process:
explorer.exe

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
• Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
• Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
• Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
• If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
• If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
• For further information on the terms used in this document, please refer to the Security Response glossary.

Summary