ENSRT Incident Note ETS-i-2005-12527
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.BA@mm
Release Date: 02/21/2005
Last Updated: 02/22/2005
Overview
W32.Mydoom.BA@mm is a mass-mailing worm that retrieves addresses from the Windows Address Book on the infected computer and uses an embedded SMTP engine to further proliferate the worm. Additionally, the worm downloads a backdoor component allowing for execution of commands by a remote malicious user.
Also known as:
Email-Worm.Win32.Mydoom.am , WORM_MYDOOM.BA
Details below will describe the characteristics of the W32.Mydoom.BA@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
W32.Mydoom.BA@mm mass mailer arrives in the user mailbox as an e-mail with one of the following subject lines:
- "hello"
- "hi"
- "error"
- "status"
- "test"
- "report"
- "delivery failed"
- "Message could not be delivered"
- "Mail System Error - Returned Mail"
- "Delivery reports about your e-mail" -
- "Returned mail: see transcript for details"
- "Returned mail: Data format error delivered"
The message body of the e-mail is generated using strings that are harvested from the user’s system. The worm randomly chooses a message inserting a wide array of variables in an effort to evade common pattern matching techniques.
The W32.Mydoom.BA@mm worm uses a filename generated from an email address that it finds on the compromised computer or one of the following:
- "ATTACHMENT"
- "DOCUMENT"
- "FILE"
- "INSTRUCTION"
- "LETTER"
- "MAIL"
- "MESSAGE"
- "README"
- "TEXT"
- "TRANSCRIP"
and appends one of the folowing extensions:
- ".bat"
- ".cmd"
- ".com"
- ".exe"
- ".pif"
- ".scr"
- ".zip"
The attachment may have a second extension, which will be one of the following:
- "doc'
- "txt"
- "htm"
- "html"
Next, the W32.Mydoom.BA@mm worm gathers email addresses from the Windows Address Book as well as from GET requests to the following Internet search engines:
search.yahoo.com
search.lycos.com
www.altavista.com
www.google.com
Once the e-mail addresses have been collected the worm uses an embedded SMTP engine to further rpoliferate itself.
Finally, the W32.Mydoom.BA@mm worm downloads the Backdoor.Nemog.D trojan from one of several websites and launches it. This component opens TCP port 1132 for listening and waits for commands from a remote malicious user. The following websites are utilized to access the backdoor download:
- "www.imogenheap.co.uk"
- "www.newgenerationcomics.net"
- "www.aartanridge.org.uk"
- "www.eastcoastchoons.co.uk"
- "www.foxalpha.com"
- "www.sundayriders.co.uk"
- "www.hooping.org"
- "www.ribaforada.net"
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.BA@mm worm can be retrieved via Dragon Live Update and are located in the Master Library within the ENSRT category. The signatures listed with the prefix "ENSRT:W32-MYDOOM-BA", detect the infected user as it attempts to download a backdoor program from one of the websites listed in the "Description" section of this report.
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 quarentine 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.
Apply the below available NetSight PMD file and apply the policy to user ports to block the W32.Mydoom.BA@mm worm's backdoor listener.
This NetSight PMD file can be downloaded from here: http://www.enterasys.com/support/pmd.html?12527
Note: www.iana.org website lists TCP port 1132 unassigned. Apply this PMD file only if TCP port 1132 traffic is not used within the enterprise.
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.
Scan all clients and servers for newly opened TCP ports that did not appear in previous TCP scans. If viruses are detected apply appropriate removal tools on each client and server that have the open ports (See your anti-virus solution for removal instructions).
References
http://securityresponse.symantec.com/avcenter/venc/data/w32.mydoom.ba@mm.html
http://www.iana.org/assignments/port-numbers
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM%5FMYDOOM%2EBA
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: 02/21/2005 |
Author: ENSRT STAFF |
Change |