Net-Worm.Win32.BlueCode

Parent class: VirWare

Viruses and worms are malicious programs that self-replicate on computers or via computer networks without the user being aware; each subsequent copy of such malicious programs is also able to self-replicate. Malicious programs which spread via networks or infect remote machines when commanded to do so by the “owner” (e.g. Backdoors) or programs that create multiple copies that are unable to self-replicate are not part of the Viruses and Worms subclass. The main characteristic used to determine whether or not a program is classified as a separate behaviour within the Viruses and Worms subclass is how the program propagates (i.e. how the malicious program spreads copies of itself via local or network resources.) Most known worms are spread as files sent as email attachments, via a link to a web or FTP resource, via a link sent in an ICQ or IRC message, via P2P file sharing networks etc. Some worms spread as network packets; these directly penetrate the computer memory, and the worm code is then activated. Worms use the following techniques to penetrate remote computers and launch copies of themselves: social engineering (for example, an email message suggesting the user opens an attached file), exploiting network configuration errors (such as copying to a fully accessible disk), and exploiting loopholes in operating system and application security. Viruses can be divided in accordance with the method used to infect a computer:

• file viruses
• boot sector viruses
• macro viruses
• script viruses

Any program within this subclass can have additional Trojan functions. It should also be noted that many worms use more than one method in order to spread copies via networks.

Class: Net-Worm

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.

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Platform: Win32

Win32 is an API on Windows NT-based operating systems (Windows XP, Windows 7, etc.) that supports execution of 32-bit applications. One of the most widespread programming platforms in the world.

Description

Technical Details

This is an Internet worm that targets Web sites by infecting Internet Information Servers (ISS). The worm perpetrates this method of spreading from one Web site to another by sending and executing its EXE file.

The name of the worm's files are consistant - SVCHOST.EXE and HTTPEXT.DLL. The EXE file is a Win32 application (PE EXE file) about 29K in length, and it is written in Microsoft C++. There also was a compressed variant discovered, which is about 14K in size. The DLL file is about 47K in size, and it is written in Microsoft C++.

Note that the worm uses standard Win32 EXE file names. SVCHOST.EXE and HTTPEXT.DLL can be found in standard Win2000 installations in the SYSTEM32 subfolder.

The worm infects only machines installed with the IIS package and Web site contents. The worm application, upon being run on a such machine, locates and infects remote Web sites (remote machines with installed IIS package): it enters them and, by using a Web Directory Traversal exploit, sends its copy there, and spawns that copy. As a result, the worm infects all vlunerable Web servers that can be accessed from current a infected machine, and other infected servers spread the worm copy further, and so on.

The worm has a payload routine that, from 10:00 am till 11:00 am global time, performs a DoS attack (Deny of Service) on the http://www.nsfocus.com Web server.

Installing

The worm creates its copies (EXE and DLL) in the root of C: drive - C:SVCHOST.EXE and C:HTTPEXT.DLL. This EXE file is then registered in the Registry auto-run key:

HKLMSoftwareMicrosoftWindowsCurrentVersionRun
Domain Manager = C:svchost.exe

The worm then creates and swapns a C:D.VBS script file, then looks for the INETINFO.EXE application and terminates it if it is active. The VBS script program also searches for Indexing Service, Indexing Query and printer mapping and removes them.

As a result, the worm disables security breaches that can be used (or were used) by other worms to infect the machine and/or hackers to break through the Web-security protections.

Spreading

To spread further, the worm runs 100 threads that scan randomly selected IP addresses and attacks them.

In 50% of the cases, the attacked machines are in the same network, and the attacked IP addresses are "aa.bb.??.??", where "aa.bb" is part of the infected machine IP address, and "??" are random.

In the other 50% of the cases, the attacked addresses are very random.

To attack a victim machine, the worm uses the Web Directory Traversal exploit three times:

1. it tries to determine the IIS directory on a remote machine,
2. then sends a request to the remote machine to download the DLL component of the virus (HTTPEXT.DLL file) from the infected one,
3. the last request is to copy that DLL file to the C: root directory.

To upload a DLL file to a victim machine, the worm uses a "tftp" command, and activates the temporary TFTP server on an infected (current) machine to process a "get data" command from the victim (remote) machine.

When a DLL file is uploaded to the victim machine, it is activated by a trick. So, the worm copy starts on a remote server, then it drops and executes the EXE component that then spreads the virus futhrer.

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