Virus Database

YCTC family

Description YCTC family

These are very dangerous memory resident parasitic viruses. They hook INT 21h, 2Fh. INT 2Fh hook is used for stealth. INT 21h hook is used for infection - the viruses write themselves to the end of COM and EXE files that are executed or opened. They do not infect files with names that start with:
"YCTC.1729": COMMAND IBM ET PC TB CKVI KLVI DEVI BTOOL
RTOOL TDISK SCAN CLEAN HUNT F- TR G
"YCTC.1975": COMMAND LIU2 EMM386 JEAN RAR VTHUNT VTSCAN

"YCTC.1729" uses anti-debugging tricks. It deletes the files with names that start with 'Z' letter, or if directory name starts with 'Z', then it displays the message:
You have a Y.C.T.C.Virusall Ha! Ha! Ha! Ha!
== Written by Y.C.T.C.student 1995. ==
=== I am y.c.t.c. student written... ===

"YCTC.1975" corrupts the files while infecting them (i.e. it is "intended" virus). Depending on the system date it deletes the files, displays the messages in Chinese and English:
Hello !! I am a cute virus baby.
You can call me [ YCTC ] virus..
Come on,to go to study YCTC school !!
Written by Jean 1995.08.01.
Happy birthday to my dear !!
Written by Jean 1995.08.01.

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IIS-Worm.IISWorm

Description IIS-Worm.IISWorm

This is the first known worm intending to target Web sites by infecting Internet Information Servers (ISS). The worm realizes its method of spreading from one Web site to other Web sites by sending and executing its EXE file. The name of the worm file is constant - IISWORM.EXE.
The worm infects only machines with an installed IIS package and Web-site contents. The worm application 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 trick, sends its copy to there, and spawns that copy in there. As a result, the worm infects all Web servers that can be accessed from the currently infected machine, and other infected servers spread the worm copy further etc.
A similar way of infection was used by the famous "Morris virus" (a.k.a. "Internet worm") that hit USA networks back in 1988. That worm infected several thousand machines and paralyzed many networks because of unlimited copies sent. Fortunately, the "IISWorm" has a lethal bug and cannot repeat that story. The worm seems to be able to spread its copy to the first IIS machine, but fails to spread itself further.
The worm code contains only spreading routines, not trigger ones. The worm does not manifest itself in any way.
The worm itself is a Win32 application about 80K in length, written in Borland C++. It is executed as a standard Windows application, opens a connection and uses an HTTP-packets format to spread itself.
To locate victim servers, the worm looks for Web-site addresses in all *.HTM* files in the INetpub directories:
wwwroot
www root
inetpubwwwroot
inetpubwww root
websharewwwroot
By using Web-site addresses, the worm connects them and sends a bomb package to there. This package exploits a vulnerability in IIS software - the package is constructed so that its data overlaps a data buffer on a remote IIS, and a block of the package is executed as code in there (at a remote IIS). This piece of code opens a connection to its "parent" machine, gets the complete copy of the worm (the IISWORM.EXE file), creates it on a disk and spawns. As a result, the remote IIS machine is infected and the worm is active in it and continues spreading.
During tests in the lab, there were some mistakes found in the worm code that prevent the worm from spreading. The worm seems also to be dependent on the IIS and WinNT ServicePack versions.

Ilja.1704

Description Ilja.1704

It is a dangerous memory resident parasitic virus. It hooks INT 16h, 21h and writes itself to the end of .COM files that are executed. There is the word "CR" at the beginning of infected files. By hooking INT 16h this virus checks the keys that are pressed. If the word "ilja" is entered, the virus reboots the computer.

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