ENSRT Incident Note ETS-i-2005-12581
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.Mytob.EH, EK, EO, and EP
Release Date: 06/14/2005
Last Updated:
Overview
W32.Mytob.EH, EK, EO, and EP are mass-mailing worms that retrieve e-mail addresses from the Windows Address Book and system files on the infected computer and use an embedded SMTP engine to further proliferate. Additionally, the worms open an IRC backdoor connection to various Internet based IRC servers allowing for possible remote access to the conquered PC.
Details below describe the characteristics of the W32.Mytob.EH, EK, EO, and EP worms 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
Worms W32.Mytob.EH, EK, EO, and EP arrive via an e-mail with attachment in the user's mailbox using either a randomly generated Subject line or one of the following:
- Your password has been updated
- Your password has been successfully updated
- You have successfully updated your password
- Your new account password is approved
- Your Account is Suspended
- *DETECTED* Online User Violation
- Your Account is Suspended For Security Reasons
- Warning Message: Your services near to be closed
- Important Notification
- Members Support
- Security measures
- Email Account Suspension
- Notice of account limitation
Worms W32.Mytob.EH, EK, EO, and EP also contains one of the following message bodies:
- "Dear user [$username],
You have successfully updated the password of your [$domain] account.
If you did not authorize this change or if you need assistance with your
account, please contact [$domain] customer service at: [$fulldomain]
Thank you for using [$domain]!
The [$domain] Support Team"
- "Dear user [$username],
It has come to our attention that your [$domain] User Profile ( x )
records are out of date. For further details see the attached document.
Thank you for using [$domain]!
The [$domain] Support Team
+++ Attachment: No Virus (Clean)
+++ [$domain] Antivirus - www.[$fulldomain]"
- "Dear [$domain] Member,
We have temporarily suspended your email account [$username].
This might be due to either of the following reasons:
1. A recent change in your personal information (i.e. change of address).
2. Submiting invalid information during the initial sign up process.
3. An innability to accurately verify your selected option of
subscription due to an internal error within our processors.
See the details to reactivate your [$domain] account.
Sincerely,The [$domain] Support Team
+++ Attachment: No Virus (Clean)
+++ [$domain] Antivirus - www.[$fulldomain]"
- "Dear [$domain] Member,
Your e-mail account was used to send a huge amount of unsolicited spam
messages during the recent week. If you could please take 5-10 minutes
out of your online experience and confirm the attached document so you
will not run into any future problems with the online service.
If you choose to ignore our request, you leave us no choice but to cancel
your membership.
Virtually yours,
The [$domain] Support Team
+++ Attachment: No Virus found
+++ [$domain] Antivirus - www.[$fulldomain]"
If the attachment contained within the W32.Mytob.EH, EK, EO, or EP e-mail 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.
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 embedded IRC bot which connects to an IRC server on various Internet based IRC servers and awaits 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 W32.Mytob.EH, EK, EO, and EP worms 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:W32-MYTOB-EH" 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:W32-MYTOB-EH" family 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.
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.mytob.eh@mm.html
http://securityresponse.symantec.com/avcenter/venc/data/w32.mytob.ek@mm.html
http://securityresponse.symantec.com/avcenter/venc/data/w32.mytob.eo@mm.html
http://securityresponse.symantec.com/avcenter/venc/data/w32.mytob.ep@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:
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Version: 1.0 |
Date: 06/14/2005 |
Author: ENSRT STAFF |
Change |