|Detected||May 24 2001 20:00 GMT|
|Released||May 24 2001 20:00 GMT|
|Published||May 31 2001 11:03 GMT|
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.
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 worm's components.
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 demon: "named".
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 ADM Inet w0rm is here !
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".
Net-Worms propagate via computer networks. The distinguishing feature of this type of worm is that it does not require user action in order to spread.
This type of worm usually searches for critical vulnerabilities in software running on networked computers. In order to infect the computers on the network, the worm sends a specially crafted network packet (called an exploit) and as a result the worm code (or part of the worm code) penetrates the victim computer and activates. Sometimes the network packet only contains the part of the worm code which will download and run a file containing the main worm module. Some network worms use several exploits simultaneously to spread, thus increasing the speed at which they find victims.