Net-Worm.Win32.Lovesan

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

Lovesan is an Internet Worm which exploits the DCOM RPC vulnerability in Microsoft Windows described in MS Security Bulletin MS03-026.

Lovesan is written in C using the LCC compiler. The worm is a Windows PE EXE file about 6KB (compressed via UPX - 11KB when decompressed).

Lovesan downloads and attempts to run a file named msblast.exe.

The text is as follows:

I just want to say LOVE YOU SAN!!
billy gates why do you make this possible? Stop making money and fix your software!!

Symptoms of Infection:

• MSBLAST.Exe in the Windows system32 folder.
• Error message: RPC service failure. This causes the system to reboot.

How the Worm Spreads

Lovesan registers itself in the autorun key when the system reboots and launches itself every time the computer reboots in the future:

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun



windows auto update="msblast.exe"

The worm then scans IP addresses, attempting to connect to 20 random IP addresses and infect any vulnerable machines. Lovesan sleeps for 1.8 seconds and scans the next 20 IP addresses.

Lovesan scans IP addresses following one of the patterns below:

1. In 3 out of 5 cases Lovesan selects random base IP addresses (A.B.C.D) where D is equal to 0, while A, B and C are random numbers between 0 and 255.
   
   
2. In the remaining 2 out of 5 cases Lovesan scans the subnet and gets the local IP address of the infected machine, extracts values A and B from it and sets D to 0. Then the worm extracts the C value.

   If C is less than or equal to 20, then Lovesan does not modify C. Thus, if the local IP address is 207.46.14.1 the worm will scan IP addresses starting from 207.46.14.0

   If C is greater than 20, than Lovesan selects a random value between C and C-19. Thus, if the IP address of the infected machine is 207.46.134.191 the worm will scan IP addresses 207.46.{115-134}.0

The worm sends a buffer-overrun request to vulnerable machines via TCP port 135. The newly infected machine then initiates the command shell on TCP port 4444.

Lovesan runs the thread that opens the connection on port 4444 and waits for FTP 'get' request from the victim machine. The worm then forces the victim machine to sends the 'FTP get' request. Thus the victim machine downloads the worm from the infected machine and runs it. The victim machine is now also infected.

Other Information

Once a computer is infected the system sends an error message about RPC service failure and may reboot the machine.

As of August 16, 2003 Lovesan will launch DDoS attacks on the Windowsupdate.com server.

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Find out the statistics of the vulnerabilities spreading in your region on statistics.securelist.com