ENSRT Incident Note ETS-i-2005-12517

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.

W32.Crowt.A@mm

Release Date: 01/24/2005
Last Updated:

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Overview

W32.Crowt.A@mm is a mass mailing worm that attempts to email itself to all addresses found in the Microsoft Outlook Address Book of the infected computer. It also provides backdoor and keystroke logging functionality as well as the ability to send gathered data to a remote user

Also known as: W32/Crowt-A [Sophos], WORM_CROWT.A [Trend Micro]

Systems affected

Systems not affected

Description

When W32.Crowt.A@mm is executed, it performs the following actions:
- Creates files named "services.exe" in several locations,
- Adds values to the registry keys so that the worm is executed each time Windows is started
- Opens a browser page to "www.cnn.com"
- Logs keystrokes and clipboard data to a file which is later emailed to the attacker
- Opens a back door by connecting to the host "cocoazul.ath.cx"
- Attempts to connect to web sites on the domains "www.cocorosa.ath.cx" and "www.cocoazul.ath.cx" through TCP port 137 (Note: TCP is registered for NETBIOS Name Service )
- Listens for commands that enable a remote attacker to perform various actions
- Uses its own SMTP engine to send itself to the email addresses that it finds in the Microsoft Outlook Address Book.
The email message and body may contain information such as headlines of the Web site "www.cnn.com/WORLD". The email attachment may contain the file "SERVICES.EXE", which is a copy of this worm itself.

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

Detection

Updated IDS signatures can be downloaded here: https://dragon.enterasys.com/ (requires login)

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

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.

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.

Note: The two domains www.cocoazul.ath.cx and www.cocorosa.ath.cx are not available at this time. If these addresses do become available in the future, a Enterasys Policy Manager pmd file will be made available for download.

Repair

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).

Monitor SMTP mail server logs to locate infected users sending multiple copies of the worm e-mail matching the previously defined subject and body. Once isolated, see your anti-virus vendor for Windows repair procedures for infected users.

References

http://www.iana.org/assignments/port-numbers
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM%5FCROWT%2EA
http://securityresponse.symantec.com/avcenter/venc/data/w32.crowt.a@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:

Version: 1.0

Date: 01/24/2005

Author: ENSRT STAFF

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