ENSRT Incident Note ETS-i-2005-12529
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_AHKER.E
Release Date: 02/24/2005
Last Updated:
Overview
WORM_AHKER.E propagates via SMTP by using social engineering to entice people to download an attachment that contains the worm. This worm will then rapidly spread using two methods: through e-mail messages sent via SMTP and through peer to peer file sharing networks.
Also known as:
W32.Ahker.D@mm, W32/Ahker-E, W32/Generic.d, Win32.Ahker.E
Details below will describe the characteristics of WORM_AHKER.E 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
WORM_AHKER.E sends copies of itself through email messages using Simple Mail Transfer Protocol (SMTP). The email message it sends erroneously purports to be from either Symantec or Trend Micro and contains content warning the user that they are indeed infected with the AHKER. E worm. The message strongly suggests that the user access the attached executable named "Removal Tool.zip". The embedded executable will cause the worm to be launched.
Once launched, the worm performs several tasks. First, it copies itself into the Windows folder and changes registry settings so that it is launched each time the infected PC starts.
Second, the worm drops a copy of itself in all of the system's shared folders and changes registry entries to share the worm to P2P networks. The worm renames itself with what are considered enticing executable names in order to persuade remote attached users to voluntarily download and execute the attachment.
Third, the worm spreads copies of itself via IRC. It drops a SCRIPT.INI file to mIRC folders of the affected system. This then sends a copy of worm to any remote user who joins the same IRC channel to which the user connects.
Fourth, the worm modifies registry entries in an attempt to freeze Windows security protection and modifies the Hosts file in order to stop users' ability to access many security related websites. It also terminates many popular malware programs and certain security and antivirus applications.
Finally, This worm changes the affected system's computer name to Agent Hacker. It also overwrites "WINWORD.EXE"(Microsoft Word) in order to execute once the user attempts to open a .DOC file or Microsoft Word itself.
Note: The WORM_AHKER.E can also perform a DoS attack against "www.windowsupdate.microsoft.com" using ICMP flooding:
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 AHKER.E worm can be retrieved via Dragon Live Update and is located in the Master Library within the ENSRT category. This signature, "ENSRT:AHKER-E-001" can be copied into a custom library.
Deploying the above signature on a Dragon network sensor that is monitoring the enterprise SMTP server can successfully detect end-user class machines which have become infected with the worm.
If utilizing Dynamic Intrusion Response (DIR), a Dragon Alarmtool policy that consists of an event group containing the "ENSRT:AHKER-E-001" signature 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.
If acceptable use policy does not allow for the use of IRC, dragon signatures are available within the master library to detect the existence of IRC traffic.
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.
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.
References
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM%5FAHKER%2EE&VSect=P
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Revision History:
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Version: 1.0 |
Date: 02/24/2005 |
Author: ENSRT STAFF |
Change |