Summary

Disinfection instructions for Aliz worm can be found here:

http://www.europe.f-secure.com/v-descs/aliz_dis.shtml




Aliz worm became widely spread in the end of November 2001. The worm activates automatically while reading an infected email message.

Aliz is a very small e-mail worm written in pure Assembly. The worm's file is only 4 kilobytes long and its code is compressed. It can be considered one of the smallest Win32 worms ever created.

When the worm is run, it first unpacks itself and then passes control to API address setup routine. When all needed API addresses are collected, the control is passed to the main worm's code. The worm checks the Registry for the location of Windows Address Book file and loads it into memory. The worm then connects to default SMTP server (for SMTP server info the worm checks Internet Account Manager data in the Registry) and sends itself to all recepients of Windows Address Book. The infected message looks like that:

 Subject: <randomly composed from several different parts, see below>
 Body: <empty multi-part MIME message with HTML formatting and i-frame trick>
 Attachment: Whatever.exe

The subject of infected message is randomly composed from 5 (sometimes less) different parts:

 Fw:
 Fw: Re:

 Cool
 Nice
 Hot
 some
 Funny
 weird
 funky
 great
 Interesting
 many

 website
 site
 pics
 urls
 pictures
 stuff
 mp3s
 shit
 music
 info

 to check
 for you
 i found
 to see
 here
 - check it

 !!
 !
 :-)
 ?!
 hehe ;-)

For example a subject can be: "Fw: Cool pictures i found !!" or "Nice website to check hehe ;-)".

The message contains a MIME-encoded attachment - the worm's file with 'Whatever.exe' name. The body is an empty multi-part MIME message with HTML formatting and i-frame trick that was previously found in Nimda and Klez worms. Because of this trick on some systems the worm is able to self-launch itself when an infected e-mail is viewed (for example, with Outlook and IE 5.0 or 5.01). To do this the worm uses a known vulnerability in IE that allows execution of an email attachment. This vulnerability is fixed and a patch for it is available on Microsoft site:

http://www.microsoft.com/windows/ie/downloads/critical/q323759ie/default.asp

Some e-mail browsers where i-frame trick doesn't work can show the word 'peace' in infected e-mail message's body.

The worm doesn't install itself to system, it runs, sends itself out and terminates its process in case of errors.

The worm contains the following text strings that are never displayed:

 :::iworm.alizee.by.mar00n!ikx2oo1:::

 while typing this text i realize this text got added on many av
 description sites, because this silly worm could be easily a
 hype. i wonder which av claims '[companyname] stopped high risk
 worm before it could escape!' or shit like that. heh, or they
 boycot my virus because of this text. well, it is easy enough
 for the poor av's to add this worm; since it was only released
 as source in coderz#2... btw, loveletter*2 power in pure win32asm
 and only a 4k exe file. heh, vbs kiddies, phear win32asm. :)
 thx to: bumblebee!29a, asmodeus!ikx. greets to: starzer0!ikx,
 t-2000!ir, ultras!mtx & sweet gigabyte...
 btw,burgemeester van sneek: ik zoek nog een baantje...
 (alignmentfillingtext)

F-Secure Anti-Virus detects Aliz worm since May 2001.

[Analysis: Alexey Podrezov; F-Secure Corp.; November 19th, 2001]