ENSRT Incident Note ETS-i-2005-12518

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.Ahker.B@mm

Release Date: 01/26/2005
Last Updated: 01/27/2005

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Overview

W32.Ahker.B@mm is a mass-mailing worm that is written in Visual Basic and will send itself to all addresses in the Windows address book of the conquered system. The worm also disables several Windows security features and system processes.

Also Known As: WORM_AHKER.B [Trend Micro]

Systems affected

Systems not affected

Description

This variant of the WORM_AHKER family mainly propagates through email. It arrives in a users mailbox with a subject line of "Service Pack 2 BUG!!", and in the "Message Body" entices the user to execute the attached file.

Upon execution the worm will perform the following:

- Terminates a series of processes including several related to anti-virus and security applications
- Makes changes to the hosts file to prevent access to certain websites
- Downloads the file ahkerb.zip from the geocities.com domain and saves it as C:\Fix_SP2.zip.
- Uses MAPI to send email to all addresses in the Windows Address Book.
- Once mail has been sent the file "C:\Fix_SP2.zip" is deleted.
- Creates copies of itself in several directories, named services.exe
- Creates/changes values to registry keys so that it runs when Windows starts, attempts to run when a user opens a ".txt" file, disables some Windows security features including Auto Update and the Windows Firewall, and terminates the following programs and processes:

Task Manager
Registry Editor (regedit.exe)
Notepad (notepad.exe)
Wordpad (wordpad.exe, write.exe}
Windows Update (wuauclt.exe, wupdmgr.exe )
MSN Messenger (msnmsgr.exe)
SVCHOST.exe
LSASS.exe

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

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.

Repair

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://securityresponse.symantec.com/avcenter/venc/data/w32.ahker.b@mm.html
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM_AHKER.B&VSect=T

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