ENSRT Incident Note ETS-i-2005-12542

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.

Worms - W32.Kelvir.G and W32.Kelvir.H

Release Date: 03/15/2005
Last Updated: 03/16/2005

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Overview

The W32.Kelvir.G and W32.Kelvir.H worms spread via instant messages from the MSN Messenger application. These messages contain a hyperlink pointing to a website that contains a downloadable version of the worm. If the executable file is downloaded and launched, the Windows PC becomes infected with the Kelvir worm. The worm also drops a backdoor trojan onto the infected system.

Details below describe the characteristics of the W32.Kelvir worm family, as well as provide detection, containment, and prevention techniques available through Enterasys Secure Networks solutions.

Systems affected

Windows operating systems

Systems not affected

Linux and MAC/OSX

Description

The Kelvir worms arrive on the user's PC via an instant message from the MSN Messenger application containing a hyperlink to a web-based executable file from a known MSN contact. If via social engineering, the worm executable is both received and executed, the Microsoft Windows PC will become infected.

Once the file has been executed, the worm will download an executable from one of many sites determined by the worm's variant into a folder on the system and then modify the registry to ensure that it runs at each startup. This file is a variant of the Trojan W32.Spybot.Worm .

The W32.Kelvir.G and W32.Kelvir.H variants send particular MSN messages to each MSN contact on the infected machine. Each message contains a WEB based hyperlink to a copy of the worm, which if downloaded, will infect the machine. the instant message contains a link to download an executable file with the name "toosexy.pif"(variant H) or "verysexy.pif" (variant G).

Lastly, the W32.Kelvir.G worm also attempts to spread by exploiting the Microsoft SQL Server 2000 or MSDE 2000 audit and the Microsoft Windows Local Security Authority Service Remote Buffer Overflow vulnerabilities.

Threat Assessment

MSN Messenger worms if not addressed through prudent remediation steps may impact individual system performance and compromise security settings by allowing unauthorized remote access to the compromised host.

Trojans or backdoor listeners if not addressed through prudent remediation steps, can compromise network and host security. Additionally, trojans and backdoor listeners potentially allow theft of information, unauthorized remote access, and damage to critical files.

Remediation

Matrix N7	X
Matrix E7	X
Matrix E6	X
Matrix E5	X
Matrix E1	X
VH	X
C-Series	X

Detection

Specific Dragon signatures to detect the W32.Kelvir.G and W32.Kelvir.H worms can be retrieved via Dragon Live Update and are located in the Master Library within the ENSRT category. The signatures containing the prefix's "ENSRT:W32-KELVIR-G-001" and "ENSRT:W32-KELVIR-H-001" can be copied into a custom library and deployed on a Dragon network sensor that is protecting traffic flows to the Internet to successfully detect end-user class machines which have become infected with the worm.

NOTE: All signatures in the ENSRT library are disabled by default. These signatures must be enabled after they are imported into a custom library if they are to be successfully deployed.

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

The Enterasys Dynamic Intrusion Response (DIR) solution can be utilized to remove infected end-users from the enterprise network by detecting the infection with a Dragon NIDS signature (see "Detection" section of this report), locating the user's connection point using Automated Security Manager's location services module, and either placing the user in a quarantine VLAN or disabling the associated switch port for the user.

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.

Repair

Monitor Dragon Realtime Console for alerts that end-user PCs have become infected with the virus. If utilizing the DIR solution, users can either be expunged from the network or placed in a quarantine VLAN. Once isolated, see your anti-virus vendor for Windows repair procedures for infected users.

References

http://securityresponse.symantec.com/avcenter/venc/data/w32.kelvir.g.html
http://securityresponse.symantec.com/avcenter/venc/data/w32.kelvir.h.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: 03/15/2005

Author: ENSRT STAFF

Change

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