ENSRT Incident Note ETS-i-2005-12516

The Enterasys Networks Security Response Team (ENSRT) publishes incident notes to provide information for our constituents to raise awareness of issues deemed threatening to the security and integrity of our customers.

W32.Zar.A@mm

Release Date: 01/19/2005
Last Updated: 01/20/2005

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Overview

W32.Zar.A@mm is a mass-mailing worm written in Visual Basic that uses MAPI to send an email to all addresses in the Microsoft Outlook Address Book in an attempt to propagate. If successfully loaded the conquered system will launch a denial of service attack on the domain www.hacksector.de.

Also known as: W32/VBSun-A [Sophos], WORM_ZAR.A [Trend Micro]

Systems affected

Systems not affected

Description

W32.Zar.A@mm mass mailing worm arrives as an email with a subject of "Tsunami Donation! Please help" and contains an executable called "tsunami.exe" as well as a message that states "Please help us with your donation and view the attachment below! We need you!"

Upon execution of the attachment, the worm will create files, and add bogus values to a registry key in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\run directory to insure that the worm is executed each time the concurred PC is started.

Secondly, the worm attempts to perform a denial of service attack against the domain www.hacksector.de which resolves to the address 69.56.194.42.

Lastly, W32.Zar.A@mm uses MAPI to send an email to all addresses it finds in the Microsoft Outlook Address book in an attempt to further propagate the worm.

Threat Assessment

Mass-mailing worms if not addressed through prudent remediation steps may congest mail servers and/or degrade network performance. Mass-mailing worms may impact individual system performance and compromise security settings allowing unauthorized remote access to the compromised host.

Remediation

Detection

Updated IDS signatures can be downloaded here: https://dragon.enterasys.com/ (requires login)

Prevention

Trusted End System solutions are capable of monitoring various end system activity. TES is able to take immediate action such as firewalling specific IPs, TCP/UDP ports, applications, or placing the user into a Quarantine policy or VLAN until end system threat is mitigated. Learn more at: http://www.enterasys.com/solutions/secure-networks/trusted_end_system/

Containment

Internet or edge facing firewalls should be configured with a default 'Deny' policy and contain 'Permit' policies for only needed services and applications. Furthermore, careful inspection of firewall policies that allow TCP traffic streams to be initiated from the Internet into internal enterprise resources is required. These policies should only allow specific protocols to trusted servers thereby combating the increased use of random TCP ports by Internet Trojans and worms.

Using Enterasys Policy Manager, enforce a policy that allows SMTP traffic from end user PCs to authorized SMTP mail servers and blocks SMTP traffic to unauthorized end users or unknown Internet systems. If the SMTP protocol is not implemented for end users within the enterprise, consider implementing a policy blocking SMTP traffic from end user ports.

Apply the below available NetSight PMD file and apply the policy to user ports to block the W32.Zar.A@mm.

This NetSight PMD file can be downloaded from here: http://www.enterasys.com/support/pmd.html?12516

Repair

Scan all clients and servers for newly opened TCP ports that did not appear in previous TCP scans. If viruses are detected apply appropriate removal tools on each client and server that have the open ports (See your anti-virus solution for removal instructions).

Monitor SMTP mail server logs to locate infected users sending multiple copies of the worm e-mail matching the previously defined subject and body. Once isolated, see your anti-virus vendor for Windows repair procedures for infected users.

References

http://www.iana.org/assignments/port-numbers
http://securityresponse.symantec.com/avcenter/venc/data/w32.zar.a@mm.html

This document and the information contained herein are intended solely for informational use. Enterasys Networks, Inc. makes no representations or warranties of any kind, whether expressed or implied, with respect to this information and assumes no responsibility for its accuracy or completeness. Enterasys Networks, Inc. hereby disclaims all liability and warranty for any information contained herein and all the material and information herein exists to be used only on an "as is" basis. More specific information may be available on request. By your review and/or use of the information contained herein, you expressly release Enterasys from any and all liability related in any way to this information.    

A copy of the text of this section is an uncontrolled copy, and may lack important information or contain factual errors. All information herein is Copyright ©Enterasys Networks, Inc. All rights reserved. All information above is subject to change without notice.    

Revision History:

Version: 1.0

Date: 01/19/2005

Author: ENSRT STAFF

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