ENSRT Incident Note ETS-i-2005-12573
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.Mydoom.BT@mm
Release Date: 05/16/2005
Last Updated:
Overview
W32.Mydoom.BT@mm is a mass-mailing worm that retrieves e-mail addresses from the Windows Address Book on the infected computer and uses the SMTP Protocol to further proliferate. Additionally, the worm also opens an IRC back door on TCP port 6677.
Details below will describe the characteristics of the W32.Mydoom.BT@mm worm 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.Mydoom.BT@mm mass mailer arrives in the user's mailbox using a wide array of spoofed e-mail addresses and an e-mail subject line that will contain one of the following:
- Notice: **Last Warning**
- Your email account access is restricted
- Your Email Account is Suspended For Security Reasons
- Notice:***Your email account will be suspended***
- Security measures
- Email Account Suspension
- *IMPORTANT* Please Validate Your Email Account
- *IMPORTANT* Your Account Has Been Locked
The e-mail will include one of the following bodies:
- Once you have completed the form in the attached file , your account records will not be interrupted and will continue as normal.
- To unblock your email account acces, please see the attachment.
- Follow the instructions in the attchment.
- We have suspended some of your email services, to resolve the problem you should read the attached document.
- To safeguard your email account from possible termination, please see the attached file.
- please look at attached document.
- Account Information Are Attached!
The e-mail will also contain one of the following attachments with one of the following extensions .pif .scr exe .cmd or .bat.
- email-doc
- info
- text
- doc
- your_details
- document_full
- INFO
- IMPORTANT
- info-text
If the attached executable is launched the PC will become infected and the W32.Mydoom.BT@mm worm will drop a copy of itself into the Windows system folder as "LienVandeKelder.exe" and edit the system registry so that the worm is run at Windows system startup. In addition, the W32.Mydoom.BT worm opens a back door by connecting to an IRC channel on the "blackcarder.net" domain using TCP port 6677. This allows a remote attacker to download and execute files, perform a host of other IRC commands, or simply reboot the compromised computer.
The W32.Mydoom.BT@mm worm also ends many security related processes on the infected PC as well as rewrites the system "hosts" file in order to block access to security related web sites.
The W32.Mydoom.BT@mm worm then gathers e-mail addresses from several locations including the Windows Address Book and sends multiple copies of itself to each contact on the list with an embedded SMTP engine.
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.Mydoom.BT@mm worm can be retrieved via Dragon Live Update and are located in the Master Library within the ENSRT category. 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.
Note: Due to the similiarities between the Mydoom "BT" and "BO" variants, the previously created signatures for the "BO" variant will also detect "BT". Additionally, worms "WORM_MYTOB.EK" and "WORM_MYTOB.EG" will also be detected with the "ENSRT:W32-MYDOOM-BO" signatures.
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-MYDOOM-BO" 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.
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.mydoom.bt@mm.html
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM%5FMYTOB%2EEK
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM%5FMYTOB%2EEG
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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: 05/16/2005 |
Author: ENSRT STAFF |
Change |