This is the worm infecting Linux systems. The worm was discovered in spring
1998. It spreads itself from system to system by using a Linux security
breach (so called “buffer overrun” breach) that allows to upload to remote
system and run there a short piece of code that then downloads and
activates the main worm component.
The worm uses a security breach in the program package BIND (Berkeley
Internet Name Domain), which is distributed in many popular UNIX packages
and provides name service for the internet.
The Worm Itself
This is multi-component worm that consist of 8 files. These files are
script programs and executable files. The script programs are “.sh” files
that are run by Linux command shell. The executable files are standard
Linux ELF executables.
The main components of the worm are script “.sh” files that are run as
hosts, and then run the rest files (additional “.sh” files and ELF
executables) to perform necessary actions.
The list of components looks as follows:
ADMw0rm Hnamed gimmeIP remotecmd gimmeRAND scanco incremental test
The spreading (infecting a remote Linux machine) is done by “buffer
overrun” attack. That attack is performed as a special packet that is sent
to a machine being attacked. The packet has a block of specially prepared
data. That block of packet’s data is then executed as a code on that
machine. That code opens a connection to infected machine, gets the rest of
worm code and activates it. At that moment the machine is infected, and
starts to spread worm further.
The worm is transferred from a machine to machine as a “tgz” archive
(standard UNIX archive) with “ADMw0rm.tgz” name, with 8 worm components
inside. While infecting a new machine the worm unpacks that package in
there, and runs the main “ADMw0rm” file that then will activate other
To get IP addresses of remote machines to attack them the worm scans the
available global network for IP addresses with computers and DNS installed
servers on it.
To attack remote system the worm uses security vulnerabilities in Linux
To upload and activate its copy on remote machine the worm “buffer overrun”
code contains the instructions that switch to “root” privileges, runs
command shell and follows the commands:
The worm has several payload and other non-infection routines.
First of all it finds on local machine starting from root directory all
“index.html” files (Web servers start pages) and replaces them with its own
“index.html” file that contains the text:
The worm deletes the “/etc/hosts.deny” file. That file contains the list of
hosts (addresses and/or Inet names) that are denied to access this system
(in case so-called TCP wrapper is used). As a result any of restricted
machines can access affected system.
When a new system is infected, the worm sends “notification” messages to
the e-mail address “email@example.com”.