ENSRT Incident Note ETS-i-2005-12577
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 - WORM_MYTOB.AR
Release Date: 06/06/2005
Last Updated:
Overview
WORM_MYTOB.AR is a mass-mailing worm that retrieves e-mail addresses from the Windows Address Book and system files on the infected computer and uses an embedded SMTP engine to further proliferate the worm.
Details below describe the characteristics of WORM_MYTOB.AR 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
WORM_MYTOB.AR arrives via an e-mail with attachment in the user's mailbox using either a randomly generated Subject line or one of the following:
- *DETECTED* Online User Violation
- *IMPORTANT* Please Validate Your Email Account
- *IMPORTANT* Your Account Has Been Locked
- *WARNING* Your Email Account Will Be Closed
- Account Alert
- Email Account Suspension
- Important Notification
- Notice of account limitation
- Notice: **Last Warning**
- Notice:***Your email account will be suspended***
- Security measures
- Your email account access is restricted
- Your Email Account is Suspended For Security Reasons
WORM_MYTOB.AR also contains one of the following message bodies:
- Once you have completed the form in the attached file , your account records will not be interrupted and will continue as normal.
- please look at attached document.
- Please read the attached document and follow it's instructions.
- Please see the attachement.
- The original message has been included as an attachment.
- To safeguard your email account from possible termination, please see the attached file.
- To unblock your email account acces, please see the attachement.
- We attached some important information regarding your account.
- We have suspended some of your email services, to resolve the problem you should read the attached document.
- We regret to inform you that your account has been suspended due to the violation of our site policy, more info is attached.
If the WORM_MYTOB.AR worm is executed, it will infect the host machine and begin the propagation process.
This process consists of the following actions:
1) The worm plants a copy of itself in the system folder of the infected machine with the name "Lien Van de Kelder.exe".
2) The worm alters the system registry in order to ensure that it runs at Windows system startup.
3) The worm gathers addresses from the host computer's Windows address book and system files and, using its own SMTP engine, sends infected e-mail to the gathered list of addresses in hopes of further propagation.
4) The worm also contains an imbedded IRC bot which connects to an IRC server on the irc.blackcarder.net domain and joins a specific channel waiting for commands from a remote attacker.
5) The worm alters the Windows "hosts" file and sets the hostnames of Internet based security companies to the loopback IP address of 127.0.0.1.
6) The worm terminates certain security related software in an effort to avoid detection.
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.
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 that detect the WORM_MYTOB.AR worm can be retrieved via Dragon Live Update and are located in the Master Library within the ENSRT category. The four signatures with the prefix "ENSRT:WORM-MYTOB-AR" combined with the five signatures with the prefix "ENSRT:W32-MYDOOM-BO" can be copied into a custom library and deployed on a Dragon network sensor that is protecting the enterprise SMTP server to successfully detect end-user class machines which have become infected with the worm.
If utilizing Dynamic Intrusion Response (DIR), a Dragon Alarmtool policy that consists of an event group that contains all of the signatures within the "ENSRT:WORM-MYTOB-AR" and "ENSRT:W32-MYDOOM-BO" families should be used. A threshold parameter of at least three signature detections within a time span of 60 seconds should be 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://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM_MYTOB.AR
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:
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Version: 1.0 |
Date: 06/06/2005 |
Author: ENSRT STAFF |
Change |