Discovered: November 01, 2003
Updated: February 13, 2007 12:13:11 PM
Also Known As: I-Worm.Mimail.f [Kaspersky], W32/Mimail.f@MM [McAfee], WORM_MIMAIL.G [Trend], Win32.Mimail.E [Computer Assoc, W32/Mimail-E [Sophos], Mimail.F [F-Secure]
Systems Affected: Windows
Due to a decreased rate of submissions, Symantec Security Response has downgraded W32.Mimail.D@mm from a Category 3 to a Category 2 as of November 9, 2003.
W32.Mimail.D@mm is a variant of W32.Mimail.C@mm that spreads by email. It is packed with UPX.
The email has the following characteristics:
Subject: don't be late! [random string of letters]
Attachment: readnow.zip (contains readnow.doc.scr)
Note : The W32.Mimail.D@mm signature was modified in definitions dated November 3, 2003 to account for the discovery of a minor variant.
Antivirus Protection Dates
- Initial Rapid Release version November 01, 2003
- Latest Rapid Release version November 04, 2019 revision 019
- Initial Daily Certified version November 01, 2003
- Latest Daily Certified version November 04, 2019 revision 065
- Initial Weekly Certified release date November 01, 2003
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.
When W32.Mimail.D@mm is executed, it does the following:
- Copies itself as %Windir%\cnfrm.exe.
Note: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.
- Add the value:
"Cnfrm32" = "%Windir%\cnfrm.exe"
to the registry key:
- Collects email address from all the files on the computer, except those with the extensions:
- Writes all the email addresses to the file, %Windir%\eml.tmp.
- Checks to see whether there is a valid Internet connection by attempting to connect to www.google.com.
- Sends email messages using its own SMTP engine. For each email address the worm gathers, it will:
- Look up the Mail Exchange (MX) record for the domain name using the DNS server of the current host. If a DNS server is not found, it will default to 18.104.22.168.
- Acquire the mail server associated with that particular domain.
- Directly contact the destination server.
The email has the following characteristics:
From: john@<current domain> (The from address may be spoofed to appear that it is coming from the current domain)
Subject: don't be late! [random sequence of letters]
Will meet tonight as we agreed, because on Wednesday I don't think I'll make it,
so don't be late. And yes, by the way here is the file you asked for.
It's all written there. See you.
[random sequence of letters]
Note: readnow.zip contains only one file, which is readnow.doc.scr.
- Performs a Denial of Service (DoS) on the following sites:
- Creates two additional files in the %Windir% folder:
- Zip.tmp: a temporary copy of readnow.zip (10,912 bytes).
- Exe.tmp: a temporary copy of cnfrm.exe (10,784 bytes).
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.
Removal using the Removal Tool
Symantec Security Response has created a tool to remove W32.Mimail.D@mm, which is the easiest way to remove this threat.
The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
- Disable System Restore (Windows Me/XP).
- Update the virus definitions.
- Run a full system scan and delete all the files detected as W32.Mimail.D@mm.
- Delete the value that was added to the registry.
1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.
Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.
Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.
For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
- "How to disable or enable Windows Me System Restore"
- "How to turn off or turn on Windows XP System Restore"
Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.
For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder ," Article ID: Q263455.
2. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
- Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
- Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).
The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.
3. Scanning for and deleting the infected files
- Start your Symantec antivirus program and make sure that it is configured to scan all the files.
- For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
- For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan all files."
- Run a full system scan.
- If any files are detected as infected with W32.Mimail.D@mm, click Delete.
4. Deleting the value from the registry
WARNING: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry ," for instructions.
- Click Start, and then click Run. (The Run dialog box appears.)
- Type regedit
Then click OK. (The Registry Editor opens.)
- Navigate to the key:
- In the right pane, delete the value below:
"Cnfrm32" = "%Windir%\cnfrm.exe"
- Exit the Registry Editor.
Writeup By: Yuhui Huang