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F-Secure Virus Information Pages: Zafi.F
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Summary
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A new variant of Zafi worm - Zafi.F is spreading. While the
original Zafi.A uses only Hungarian, the Zafi.F spreads in
email in English, Italian, Spanish, Russian, Swedish and
several other languages.
The worm sends itself in infected messages attached as .pif,
.cmd, .bat, .com or .zip file. This variant of Zafi also spreads
in P2P networks.
It can display a decoy message in message box saying
"Image format error!"
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Detailed Description
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Zafi.F spreads in FSG! packed form which is 16770 bytes in size. The body unpacks to around 30 KiB of hand-written assembly code.
System Infection
When Zafi.F is started it copies itself to the Windows System Directory with a name "AntiVirus Update.exe". This file is added
to the following registry key:
[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
"Zi5" = "%System%\AntiVirus Update.exe"
Zafi.F creates a mutex named "Zi5" for making sure that only one copy of the worm is run at the same time.
Zafi.F enumerates all the directories in the system and copies itself as either 'Adobe Acrobat 8.0 Pro.exe' or 'Windows Update Crack.exe'
to the ones that contain 'shar', 'uploa' or 'musi' in their name.
Email Propagation
Zafi.F looks into the Windows Address Book and different files and tries to gather email addresses. Files with the following extensions are checked:
- dbx
- asp
- txt
- htm
- mbx
- wab
- php
- sht
- adb
- tbb
- inb
- pmr
- fpt
- eml
Using its own SMTP engine the worm sends messages with infected attachments in many different languages. It can use different SMTP relays for sending its messages depending on the language.
For email addresses in the following domains the worms sends messages in the respective languages:
.hu .sp .se .de .at .ch .nl .fr .it .es .mx .ru
Following text is an example of english message:
From: M. Christina
Subject: msn photo ecard
commercial ecard :))
Sender name is used as a fallback if the email address doesn't have it.
Other language versions are as follows:
From: Szalai Bernadett
Subject: legszexibb megasztar foto!
szavazz ra te is!
From: N. Fernandez
Subject: broma :))
humor :))
From: H. Andersson
Subject: rolig reklam :))
haha - rolig :))
From: H. Maria
Subject: witzig reklame :))
witzig bild :D
From: R. Cornel
Subject: grappig beeld :))
een grappig reclame :D
From: B. Martin
Subject: blague :))
humour - reclame :))
From: R. Antonio
Subject: scherzo :))
comico quadro :))
From: N. Fernandez
Subject: broma :))
humor :))
From: D. Alexej
Subject: humor.ru
:D
The body message is
ImageFormat: 640x480
ImageSize: 16Kb
Message: you need to see this :))
From:
Date:
AV-Control: MSN Mail: +++ No Virus
The actual attachment is a ZIP file with name composed of the
following words:
- reklam
- megasztar
- humor
- reklame
- reclame
- funny
commercial
Inside the ZIP file, there is a copy of the worm using one of the following file extensions:
Here's a screenshot of English message:
The worm does not send emails to addresses that contain any of these
strings:
- admi
- bitde
- contact@
- eset
- -faq
- google
- help
- hotmai
- info
- linux
- kasper
- mcafe
- micro
- msn
- nod3
- panda
- sales
- secur
- service
- soft
- sopho
- subsc
- suppor
- support
- symant
- test
- trend
- use
- webm
- win
- www
Payload
Zafi.F terminates any application that has the words 'firewall' or 'virus' in it. These files are overwritten with a copy of the worm.
Several Windows tools, like Task Manager, Registry Editor are disabled when the worm is active. Zafi.F opens these files with exclusive locking
to prevent anything else from opening them.
Zafi.F has a backdoor that listens on port 2121. The worm can upload and execute file using the backdoor. |
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F-Secure Corporation |
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Last Modified: January 01, 2006
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