MHTMLRedir.Exploit

SUMMARY

This threat allows a malicious Web site to download and execute programs on your computer.

Protection

• Virus Definitions (LiveUpdate™ Weekly) December 17, 2003
• Virus Definitions (Intelligent Updater) December 12, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low
• Payload Trigger: N/A
• Payload: N/A
• Large Scale E-mailing: N/A
• Deletes Files: N/A
• Modifies Files: N/A
• Releases Confidential Info: N/A
• Degrades Performance: N/A
• Causes System Instability: N/A
• Compromises Security Settings: N/A

Distribution

• Distribution Level: Low
• Subject of Email: N/A
• Name of Attachment: N/A
• Size of Attachment: N/A
• Ports: N/A
• Shared Drives: N/A
• Target of Infection: N/A
• Time Stamp of Attachment: N/A

TECHNICAL DETAILS

This threat contains specially-crafted, HTML code that can download and execute programs without prompting you. This threat only affects Microsoft Internet Explorer.

When visiting a Web page or receiving an HTML email that contains this threat, a file can be downloaded and executed. Under normal conditions, Internet Explorer would prompt you before allowing any executable content to be downloaded and executed on the system. This vulnerability in Internet Explorer allows specially crafted HTML to bypass this security prompt.

This detection prevents HTML files containing this vulnerability from being executed.

Microsoft has released patch MS04-013 to address this issue.

Recommendations

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

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

Because this is an exploit only, there are no removal instructions, since there is nothing to remove. This is a detection for the exploit, preventing the execution of malicious content on your computer. By detecting the exploit, it is prevented from running.