ENSRT Incident Note ETS-i-2005-12539
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.
Worm - W32.Chod@mm
Release Date: 03/14/2005
Last Updated:
Overview
W32.Chod@mm is a Microsoft Windows mass-mailing worm containing an executable attachment that spreads via an embedded SMTP engine as well as through MSN Messenger.
Details below will describe the characteristics of W32.Chod@mm as well as provide detection, containment, and prevention techniques available through Enterasys Secure Networks solutions.
Systems affected
Windows operating systemsSystems not affected
Linux and MAC/OSXDescription
The W32.Chod@mm arrives as an e-mail attachment or as an executable sent through MSN Messenger. As an e-mail it arrives under the following subject lines:
- Warning - you have been infected!
- Your computer may have been infected
As a MSN attachment the worm attempts to use the following messages as a means of social engineering to convince the user to download and run the executable file:
- lol check this out, it freaked me out :S
- LOL! look at this, I can't explain it in words...
- omg check this out, it's just wrong :O
- ROFL!! you have to see this... wtf...
- you have to see this, it's amazing!
Additionally, the worm executable whether as an e-mail or MSN messenger attachment, makes use of enticing filenames to further enhance the possibility that the end-user will download and launch the worm.
When W32.Chod@mm is launched, registry entries are created to assure that the worm is restarted on Windows bootup. Additionally, the following four files are created in the "C:\WINDOWS\SYSTEM32" directory on the newly infected machine:
- cpu.dll
- csrss.dat
- csrss.exe
- csrss.ini
The worm then disables multiple security related programs and features on the host system through registry edits and process termination. In addition, the worm will open up a backdoor connection to an irc server to listen for commands from a remote attacker. The backdoor connection allows the remote attacker a wide range of negative behaviors including stealing passwords from instant messenger programs, launching Denial of Service attacks, and launching SMTP or MSN propagation routines.
Lastly, the W32.Chod@mm worm attempts further propagation by sending itself with an embedded SMTP engine to a list of e-mail addresses gathered from the infected machine as well as via instant messages to MSN Messenger contacts.
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.
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
A specific set of Dragon signatures to detect the W32.Chod@mm worm can be retrieved via Dragon Live Update and are located in the Master Library within the ENSRT category.
The first two signatures with the prefix "ENSRT:W32-CHOD-SMTP" are designed to detect the SMTP propagation of the worm and should be copied into a custom library and deployed on a Dragon network sensor that is protecting the enterprise SMTP server.
The last five signatures with the prefix "ENSRT:W32-CHOD-MSN" are designed to detect the MSN Messenger propagation of the worm and should be copied into a custom library and deployed on a Dragon network sensors that protect the pathways to the Internet.
If utilizing Dynamic Intrusion Response (DIR) with the "ENSRT:W32-CHOD-SMTP" signatures, a Dragon Alarmtool policy that consists of an event group with these two signatures should be created with a threshold parameter of at least three signature detections within a time span of 60 seconds. These settings are used to mitigate the existence of false positives.
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.
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.
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.chod@mm.html
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM%5FCHOD%2EA
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: 03/14/2005 |
Author: ENSRT STAFF |
Change |