Zafi.B

Classification

Malware

Email-Worm

W32

Zafi.B, W32/Zafi.B@mm, I-Worm.Zafi.b

Summary

A new variant of Zafi worm - Zafi.B is spreading. While the original Zafi.A uses only Hungarian, the new Zafi.B spreads in email in English, Italian, Spanish, Russian, Swedish etc.The worm sends itself in emails mostly as .pif attachment and in rare cases it sends .exe or .com.

Automatic action

Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

For more Support

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User Guide

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Contact Support

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Submit a sample

Submit a file or URL for further analysis.

Technical Details

Zafi.B spreads in FSG! packed form which is 12800 bytes in size. The body unpacks to around 30 KiB of hand-written assembly code.

System Infection

When Zafi.B is started it copies itself to the Windows System Directory with a random .DLL and random .EXE name. The .EXE file is added to the registry as

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]   "_Hazafibb" = "%SysDir%\.exe"    

Several additional files are created in the System Directory with random name and .DLL extension. The worm keeps its internal data in those.

Zafi.B enumerates all the directories in the system and copies itself as either 'winamp 7.0 full_install.exe' or 'Total Commander 7.0 full_install.exe' to the ones that contain 'share' or 'upload' in their name.

Email Propagation

Zafi.B looks into the Windows Address Book and different files and tries to gather email addresses. Files with the following extensions are checked:

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
 "_Hazafibb" = "%SysDir%\.exe"

Using its own SMTP engine the worm sends messages with infected attachments in many different languages.

For email addresses in the following domains the worms sends messages in the respective languages:

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
 "_Hazafibb" = "%SysDir%\.exe"

For Hungarian recipients there are three different messages. Any recipient that is not on the list (including .COM, .NET, etc.) is sent one of the three predefined English messages.

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
 "_Hazafibb" = "%SysDir%\.exe"

In rare cases the email will have an attachment with the name 'Surprise' and extension '.com', '.exe' or '.pif'.The worm does not send emails to addresses that contain any of these strings:

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
 "_Hazafibb" = "%SysDir%\.exe"

Payload

Zafi.B 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.B opens these files with exclusive locking to prevent anything else from opening them.