Malicious Software Encyclopedia: Win32/Dumaru
Published:
August 9, 2005
Win32/Dumaru is a family of mass-mailing worms that targets certain versions of Microsoft Windows. The worm sends itself as an e-mail attachment to addresses that it finds on the infected computer. The worm runs when the user opens the attachment. Some variants drop a backdoor Trojan. Win32/Dumaru can infect or overwrite files, open ports, connect to an IRC server, release passwords and other confidential information, and receive commands from attackers.
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Threat Overview
| Class/type | Virus - File
Worm - Mass Mailer
|
| Discovered | August 19, 2003 |
| Circulating | Yes |
| Affected operating systems | Windows NT 4.0
Windows 95
Windows 2000
Windows XP
|
| Affected software |
Not specified
|
| Infection rating | Medium |
| Recovery difficulty | Moderate |
| Damage rating | High |
| Transmission rating | Medium |
Aliases (Also Known As)
Different antivirus vendors may be using different names to refer to this malicious software. Here are some of the names currently in use by antivirus software vendors participating in the Microsoft Virus Information Alliance (VIA):
CA:
Win32.Dumaru McAfee:
W32/Dumaru@MMSymantec:
W32.Dumaru@mm Trend Micro:
WORM_DUMARU
Learn more about the
Microsoft Virus Information Alliance.
Technical Analysis
When Win32/Dumaru runs, it can copy itself to multiple locations using various file names. It modifies settings so that the worm runs each time Windows starts.
Win32/Dumaru gathers e-mail addresses from the computer, saves them to a file, and sends itself as an e-mail attachment to those addresses. Some variants encode a copy of the executable file in a script that runs if the e-mail is viewed as HTML. The following is an example of e-mail from a Win32/Dumaru variant:
From: security@microsoft.com
Subject: Use this patch immediately!
Message Body:
Dear friend , use this Internet Explorer patch now!
There are dangerous virus in the Internet now!
More than 500.000 already infected!
Attachment: patch.exe
Win32/Dumaru variants may also perform actions such as the following:
Terminate certain processes.
Provide proxy services.
Open ports to receive commands or download files from attackers.
Modify or overwrite the Windows system hosts file.
Inject code into processes such as explorer.exe and run the code. The code intercepts certain API calls so that specified files are hidden.
Run hidden instances of Internet Explorer to visit certain Web sites.
Collect information such as IP addresses, passwords, screen captures, keystrokes, and clipboard contents. The worm saves the information in log files and periodically sends it to some other location.
Infect PE-format executable files in the root directory of NTFS partitions on local or network drives using Alternate Data Streams. On FAT32 partitions, such files may be overwritten so that their original content is not recoverable except from backup files.
How to Prevent Infection
Take the following steps to help prevent infection on your system:
Enable a firewall on your computer.
Get the latest computer updates.
Use up-to-date antivirus software.
Use caution with unknown attachments.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows XP Internet Connection Firewall.
To turn on the Internet Connection Firewall in Windows XP
Click Start, and click Control Panel.
Click Network and Internet Connections, and click Network Connections. If you do not see Network and Internet Connections, click Switch to Category View.
Highlight a connection that you want to help protect, and click Change settings of this connection.
Click Advanced, and select Protect my computer and network by limiting or preventing access to this computer from the Internet.
Click OK.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. You can use the Automatic Updates feature in Microsoft Windows XP to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
To turn on Automatic Updates in Windows XP
Click Start, and click Control Panel.
Click Performance and Maintenance. If you do not see Performance and Maintenance, click Switch to Category View.
Click System.
Click Automatic Updates, and select Keep my computer up to date.
Select a setting. Microsoft recommends selecting Automatically download the updates, and install them on the schedule that I specify and setting a regular update time.
If you choose to have Automatic Updates notify you in step 5, you will see a notification balloon when new downloads are available to install. Click the notification balloon to review and install updates.
Use up-to-date antivirus software
Most antivirus software can detect and prevent infection by known malicious software. You should always run antivirus software on your computer that is updated with the latest signature files to automatically help protect you from infection. If you don't have antivirus software installed, you can get it from one of several companies. For more information, see http://www.microsoft.com/athome/security/downloads/default.mspx
Use caution with unknown attachments
Use caution before opening unknown e-mail or IM attachments, even if you know the sender. If you cannot confirm with the sender that a message is valid and that an attachment is safe, delete the message immediately, and run up-to-date antivirus software to check your computer for viruses.
How to Tell If Your Computer Is Infected
There may be no readily apparent indications that your computer is infected with a Win32/Dumaru variant. However, your computer may be infected by this worm if you notice any of the following symptoms:
Significant slowdowns during normal operation.
Increased outbound SMTP traffic.
Receiving an attachment in an e-mail that has subject lines like "Use this patch immediately!", "Important information for you. Read it immediately!"
How to Recover from Infection
Automatic Recovery
To attempt to automatically remove this threat, run one of the following removal tools:
Transmission Methods
| Method | Description |
|---|
| Mass Mailer | Sends itself as an attachment to e-mail addresses on the infected computer. |
| Social Engineering | Can activate when the user views or previews an e-mail attachment. |
Payload Information
| Payload type | Trigger | Description |
|---|
| Creates files | Infection | |
| Sends e-mails | Execution | Sends a copy of itself as an attachment to e-mail addresses on the infected computer. |
| Corrupts Data | Execution | Can overwrite the Windows system hosts file. Can infect or overwrite PE-format executable files. |
| Release information | Execution | Can release IP addresses, passwords, screen captures, keystrokes, clipboard data, and other information. |
| Compromises Security | Execution | Drops a backdoor Trojan. |
Modified Registry Entries
| Changed registry entries |
|---|
| Key | |
| Value name | |
| Old value | |
| New value | |
