W32.ASpam.Trojan

This Trojan drops a file named Amcis32.dll into the \Windows\System folder of the infected machine. It also modifies several registry keys to ensure that the Trojan will be executed at the next restart of Windows.

The Trojan has been distributed in a spoofed email message that appears as though it was sent from microsoft.com. A copy of the message follows:

From: aspam@microsoft.com
To: Microsoft; Users
Sent: Tuesday, March 21, 2000 5:16 PM
Subject: Microsoft Anti-Spam Policy

Microsoft Anti-Spamming Policy
To All Microsoft Users:

Microsoft Corporation does not endorse "spamming"!
We do not want people to receive unsolicited email.  
In the strictest sense of the definition, you can
not contact anyone via email unless that person has
specifically told you that you can contact them or
invited contact (i.e. classified ad).  This applies
to businesses, non-profit organizations, and
individuals.

We do support open communications and we feel that
99.9% percent of the Microsoft Users community
wants to hear about our new products, critical
updates, and be informed about resources that are
available on-line.

The best way to let this many people know about
the important matters, pertinent information, and
resources is via email.  Most people do not
appreciate receiving junk mail (normally without a
valid reply address and a questionable "offer"
of some kind).  However, there are some people
that are offended about receiving legitimate email
telling them about similar interest matters.

Participate in the Microsoft Anti Spam Policy and
remember YOU CAN STOP IT!!!! Here we want to say:
This is not an UCemail, because you are getting
something for free!!!

Now we are proud to announce that our best
developers have a solution to the most troublesome
Internet problem nowadays: SPAM email!!!. Let this
be the last unexpected mail message you receive.
The software included in this mail will navigate
you through the things you need to do in order to
restrain SPAM emails.

To all true Microsoft Users.... Thank you for your
time and understanding.

Sincerely,
    Adam Ross
    Director of Microsoft Anti Spam Campaign
    Microsoft Corporation 2000

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