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The Search for Den Zuk

Fridrik Skulason
Virus Bulletin, February 1991, pp.7-8
ISSN 0956-9979
February 1991

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The virus known as Den Zuk was discovered over two years ago, and infections have occasionally been reported since then. It is a boot sector virus with one major effect and one, probably unintentional, harmful side-effect.

One of the earliest reports of the virus came from Venezuela - leading to the incorrect conclusion that it was written there. The virus was instead written in Indonesia, where several related viruses are known to exist. It contains the following text message, which is not displayed.

         Welcome to the
            C l u b
        --The HackerS--
          All The Time

          The HackerS

On a computer infected with this virus, pressing Ctrl-Alt-Del will not result in a simple reboot. If the computer has a colour display, it will display a picture on the screen for a fraction of a second. The picture shows the text "DENZUKO" and an unknown logo. Pressing Ctrl-Alt-F5 will reboot the computer, without displaying this picture. Ironically, the screen-effect eases detection and reduces the virus' chance of spreading.

Seek and Destroy

It had been thought that "Den Zuk" meant "The search", a reference to the ability of the virus to seek out and destroy copies of the Brain virus. If it finds a Brain-infected diskette, it removes the infection and replaces it with a copy of itself.

Normal 360 Kbyte disks only have tracks numbered from 0 to 39, but this virus was the first to use track 40 on diskettes - a practice which is now becoming more common. The author did not cater for 1.2 Mbyte or 3.5 inch diskettes on which track 40 is used. On these diskettes, the virus will overwrite that track, possibly damaging data or programs stored there.

The volume label "(c) Brain" on a Brain-infected diskette is changed to `Y.C.1.E.R.P' - A mysterious text - but it turned out to lead directly to the author.

Den Zuk also removes another virus - which was (correctly) assumed to be an older version of itself. This variant was discovered much later, and is generally known as `Ohio'.

It is closely related to the Den Zuk virus, but it contains different text messages:

           V I R U S
              b y
          The Hackers
          Y C 1 E R P
         D E N Z U K O
         Bandung 40254

 (C) 1988, The Hackers Team....

Who is Y.C.1.E.R.P?

To a radio-amateur, `YC1ERP' looks like a call-sign. Reference to the International Callbook revealed that this call-sign had been allocated to a person in Bandung, Indonesia.

There was no proof that this person was the author of the virus - it was also possible that the genuine virus writer bore a grudge against him, and included his call-sign in the virus to discredit him.

Obviously, the easiest way to discover whether this person was indeed the author was simply to ask him. A polite letter was sent to the Indonesian radio-amateur, asking whether he was the author or not.

His reply is published here verbatim and in its entirety.

Bandung, September 20, 1990

Dear Mr. Skulason,

First, I want to introduce myself too.

Name: Denny Yanuar Ramdhani

D.O.B.: January 16. 1964

Address: Jl. Ancol Timur XII/10, Bandung 40254, Indonesia

Occupation: -Student at PAT-Komputer Institut Teknologi Bandung.

-Freelance System-Programmer.

I want to explain about names which related with viruses.

And about two viruses, DEN ZUKO and HACKERS:

The viruses were first Indonesian viruses. The designer and author is me. Viruses name is DEN ZUKO and HACKERS (not DEN ZUK and HACKER). Created on March 1988 in Bandung, Indonesia (not Venezuela, as reported in New York Times ?) The viruses were my experiment in PC operating system, low-level language, how fast its spread, and just to "say hello" to other hackers/computer users in my city (when they pressed Ctrl-Alt-Del !). I never thought or expected its spread nationwide and then worldwide. So, I was really surprised when I read 'Tempo' (Indonesian weekly news magazine) which reported about 'Den Zuk' virus (quoted from New York Times) attacked USA, cominf from Venezuela, but I'm sure it was Den Zuko. And what made me really sure it was my virus, when I checked diskette which invected by Denzuko virus with Turbo AntiVirus, IBM VirScan and Mc Afee Accociates Scanner, its reported the diskette contains 'Den Zuk' virus.The viruses have 2 versions:

Version 2 will replace version 1 and Brain virus if find, and it has immunization for version 1 and Brain. Version 1 will replace & immunize Brain virus (Pakistani Brain) The viruses have stadium level counter at 2nd sector (sector 022H) track 028H, offset 03H (1 word). So, we can count the approximation of the virus population.

Version 1 identification is hexadimal (1 word) 0FAFAh (offset 02Bh) " 2 " " " " 0537Ch (offset 040h)

About other viruses from Indonesia:

The others are modification from Den Zuko or Hackers (except file-invected-virus, like Amoeba and Mystik). Some of virus researcher, Iknow them, but I don't have their address.

For more information, maybe you can get them, if you contacy Mr P.M.Winarno, he is the editor of MikroData and InfoKomputer Magazine. His complete address is:

P. M. Winarno
Editor Mikrodata
Jl Palerah Selatan 22 Lt. 3
Jakarta 10270
Phone 62-021-5483008 ext 3211,3212

If you contact him, say hi from me. Oo, I almost forget some information:

If you want to put my statement and publish it, you can take it from this letter, all or portion of it is up to you. I have some questions too:


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