CIACTech03-001: Spamming using the Windows Messenger Service

CIACTech03-001: Spamming using the Windows Messenger Service Privacy and Legal Notice TECHNICAL BULLETIN CIACTech03-001: Spamming using the Windows Messenger Service October 29, 2002 24:00 GMT


PROBLEM:	A spam engine has been released that uses the Windows Messenger Service (not the MSN Messenger instant messaging program) to send spam messages to users. The Messenger service is active on most Windows platforms.
PLATFORM:	Windows platforms with the Messenger service active.
ABSTRACT:	The Messenger service (not to be confused with MSN Messenger) is used by applications to send messages to the user and by system managers to send messages to users within a network. A spam (unauthorized commercial mail) engine has been devised that uses this service to send messages to systems that cause a dialog box to open on a user’s desktop. The dialog boxes open without any user interaction with the system. The Messenger service should not be turned off as many programs, such as antivirus scanners, use this service to send messages to the user. Messenger dialog boxes can only hold text, cannot have links to other websites, and cannot start applications. This spam starts with a connection to port 135 so sites with firewalls that block incoming connections to the Microsoft networking ports (135, 137-139, and 445) are immune from this spam.

LINKS:
CIAC BULLETIN:	http://www.ciac.org/ciac/techbull/CIACTech03-001.shtml
OTHER LINKS:	CNN News article: http://www.cnn.com/2002/TECH/internet/10/21/pop.upspam.ap/index.html Cnet News article: http://news.com.com/2100-1001-962483.html Wired News article: http://www.wired.com/news/technology/0,1282,55795,00.html

It has been reported by online news services that a new spamming method and engine has been devised and is being made available over the Internet. The new method uses the Windows Messaging service, which should not be confused with MSN Messenger instant messaging, to send spam (unauthorized commercial mail) messages to computer systems. The Messenger service on Windows systems is provided for sending messages to the user of the system. The message window pops up in front of everything on a user’s desktop and displays the message to him. The message box will not go away until the user clicks Ok. The messenger service was designed to be used by application programs who need to send an alert to the user of the system and by system managers to send messages to everyone in a domain. It turns out that if a system is accessible from the Internet that someone can send a message to the Messenger service on a particular machine and that machine will display the message.

The message can only be text as there are no provisions within the messaging service to send pictures, active links to websites, or to execute code as is done with e-mail generated spam. However, the message appears on a user’s system without any user intervention in front of whatever the user is working on. The user does not need to have an e-mail reader or a web browser open to receive and display these messages.

Sites that have a firewall that blocks the Windows networking ports (135, 137-139, and 445) are already protected from this spam. This particular spam engine starts with a connection to port 135 rather than the NetBIOS ports (137-139 and 445) and then connects to a port above 1024 but future spam engines could use the NetBIOS ports as well. The Messenger service generally should not be disabled or shut down because different programs use it to pass messages to a user. System managers also use it to warn of impending network actions such as server shutdowns.

It is possible to use the IP Filtering feature of Windows to block the incoming connections at the machine but the filter’s options are “Permit All” or “Permit Only <list>”. To make the filter work, you must use the “Permit Only <list>” option and supply the list of all allowed open ports. TCP Filtering is part of the Advanced Properties of the TCP/IP Protocol in the Networking control panel. Note also that blocking incoming connections to ports (TCP and UDP) 135, 137-139, and 445 at a machine may prevent that machine from participating in Windows Networking. We have seen one company (www.coffeecup.com) that is offering a filter for these ports that keeps the ports open for network communications but blocks the spam messages.

CIAC services are available to DOE, DOE Contractors, and the NIH. CIAC can be contacted at:

    Voice:          +1 925-422-8193 (7 x 24)
    FAX:            +1 925-423-8002
    STU-III:        +1 925-423-2604
    E-mail:          ciac@llnl.gov
    World Wide Web:  http://www.ciac.org/
                     http://ciac.llnl.gov
                     (same machine -- either one will work)
    Anonymous FTP:   ftp.ciac.org
                     ciac.llnl.gov
                     (same machine -- either one will work)

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