ENSRT Incident Note ETS-i-2005-12534
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_ASSIRAL.C
Release Date: 03/03/2005
Last Updated:
Overview
WORM_ASSIRAL.C is proliferated as both a mass-mailing worm using the MAPI protocol as well as via engaging filenames within Windows file shares.
Also known as: W32.Assiral.B@mm
Details below will describe the characteristics of WORM_ASSIRAL.C 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 WORM_ASSIRAL.C arrives as an e-mail in the user's mailbox containing one of the following subject names:
- I LOVE YOU
- Re: Account Info
- Re: Docs
- Re: Information
- Re: Letter
- Re: Message
- Re: My Letter
- Re: Your Documents
- Re: Your Email Info
- Windows Update
And an e-mail body containing one of the following messages:
- Dear Windows User,
- Info reguarding your Email account is in the attachments.
- Information attached.
- Kindly read and reply to my LOVE LETTER in the attachments :-)
- My letter is in the attachments.
- Please download the windows update included in the attachments.
- Please read the documents included in the attachments
- The documents you requested are in the attachments.
- The letter you requested is in the attachments.
- The message is located in the attachments.
- Your email account is about to expire, please check the attachments for details.
The worm executable name, whether as an e-mail attachment or found in a Windows file share, is one of more than fifty enticing filenames named thusly in an attempt to lure the end-user into launching the malware.
When WORM_ASSIRAL.C is launched, registry entries are created to assure that the worm is restarted on Windows bootup. Additionally, the following three files are created in the "C:\" directory on the newly infected machine:
- MESSAGE_TO_AVs.txt
- MESSAGE_TO_BROPIA.txt
- MESSAGE_TO_USER.txt
Once the worm is installed, attempts are made to terminate numerous security related processes running on the infected machine.
Next, the worm attempts to download a potentially newer version of itself from the following web site:
http://www.geocities.com/
Lastly, the WORM_ASSIRAL.C worm attempts further proliferation using the MAPI mail protocol.
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.
Remediation
| Matrix N7 | X |
| Matrix E7 | X |
| Matrix E6 | X |
| Matrix E5 | X |
| Matrix E1 | X |
| VH | X |
| C-Series | X |
Detection
A specific Dragon signature to detect the WORM_ASSIRAL.C worm can be retrieved via Dragon Live Update and is located in the Master Library within the ENSRT category. Copying this signature, "ENSRT:WORM-ASSIRAL-C-001", to a Dragon custom library and deploying it on a network sensor protecting Internet connections will detect the WEB based downloading of the WORM_ASSIRAL.C.
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%5FASSIRAL%2EC
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: 03/03/2005 |
Author: ENSRT STAFF |
Change |