The CERT Coordination Center publishes incident notes to provide information about incidents to the Internet community.
Release Date: March 19, 2002
A complete revision history can be found at the end of this file.
The CERT/CC has received reports of social engineering attacks on users of Internet Relay Chat (IRC) and Instant Messaging (IM) services. Intruders trick unsuspecting users into downloading and executing malicious software, which allows the intruders
to use the systems as attack platforms for launching distributed denial-of-service (DDoS) attacks. The reports to the CERT/CC indicate that tens of thousands of systems have recently been compromised in this manner.
Reports received by the CERT/CC indicate that intruders are using automated tools to post messages to unsuspecting users of IRC or IM services. These messages typically offer the opportunity to download software of some value to the user, including
improved music downloads, anti-virus protection, or pornography. Once the user downloads and executes the software, though, their system is co-opted by the attacker for use as an agent in a distributed denial-of-service (DDoS) network. Other reports
indicate that Trojan horse and backdoor programs are being propagated via similar techniques.
Here is an example of one such message:
You are infected with a virus that lets hackers get into your machine and read ur files, etc. I suggest you to download [malicious url] and clean ur infected machine. Otherwise you will be banned from [IRC
This is purely a social engineering attack since the user's decision to download and run the software is the deciding factor in whether or not the attack is successful. Although this activity is not novel, the technique is still effective, as evidenced
by reports of tens of thousands of systems being compromised in this manner. See IN-2000-08: Chat Clients and Network Security for additional information.
As with any DDoS tool installation, the impact is twofold. First, on systems that are compromised by users running untrusted software, intruders may
These risks are not limited to the installation of DDoS agents. In fact, any time a user runs untrusted software these same dangers are present.
- exercise remote control
- expose confidential data
- install other malicious software
- change files
- delete files
The secondary impact is to the sites targeted by the DDoS agents. Sites undergoing a DDoS attack may experience unusually heavy traffic volumes or high packet rates, resulting in degradation of services or loss of connectivity altogether.
Run and maintain an anti-virus product
The malicious code being distributed in these attacks is under continuous development by intruders, but most anti-virus software vendors release frequently updated information, tools, or virus databases to help detect and recover from the malicious
code involved in this activity. Therefore, it is important that users keep their their anti-virus software up to date. The CERT/CC maintains a partial list of anti-virus vendors at
Many anti-virus packages support automatic updates of virus definitions. The CERT/CC recommends using these automatic updates when available.
Do not run programs of unknown origin
Never download, install, or run a program unless you know it to be authored by a person or company that you trust. Users of IRC and IM services should be particularly wary of following links or running software sent to them by other users, as this is a
commonly used method among intruders attempting to build networks of DDoS agents.
Understand the risks
Users are encouraged to review our "Home Network Security" tech tip, which provides an overview of risks and mitigation strategies for home users.
Site administrators are encouraged to review our report on denial of service attack technology trends, as well as our recommendations for managing the threat of denial-of-service attacks.
Trends in Denial of Service Attack Technology
Managing the Threat of Denial-of-Service Attacks
Author(s): Allen D. Householder
Copyright 2002 Carnegie Mellon University.
March 19, 2002: Initial release