This page shows details and results of our analysis on the malware W32/CIH.Spacefiller

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Threat Detail

  • Malware Type: Virus
  • Malware Sub-type: File Infector
  • Protection Added: 1998-07-01

This is a virus detection. Viruses are programs that self-replicate recursively, meaning that infected systems spread the virus to other systems, which then propagate the virus further. While many viruses contain a destructive payload, it's quite common for viruses to do nothing more than spread from one system to another.

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Malware Proliferation

This family of viruses, written in South-East Asia, first appeared in June 1998. Currently there are three known variants; and at least two of these have been found `in the wild'. The viruses infect Windows 95 files in PE format.

Win32/CIH viruses are able to split up the body of the virus code and place it within unused parts of the infected file (PE files usually contain lots of unused space).

The viruses contain a very dangerous payload, which triggers on the 26th of any month. On this date, they attempt to overwrite the flash-BIOS. If the flash-BIOS is write-enabled (and this is the case in most modern computers with a flash-BIOS) this renders the machine unusable because it will no longer boot. At the same time, they also overwrite the hard disk with garbage.

The viruses contain the following (unencrypted) strings:
.a variant: CIH v1.2 TTIT, .EXE

EXE files of the PE (Portable Executable) format.

The only way to infect a computer with a file infecting virus is to execute an infected file on the computer. The infected file may come from a multitude of sources including: floppy diskettes, downloads through an online service, network, etc. Once the infected file is executed, the virus may activate.

All Users :
Script,Batch,Macro and non memory-resident:
Use current engine and DAT files for detection and removal.

PE,Trojan,Internet Worm and memory resident :
Use specified engine and DAT files for detection. To remove, boot to MS-DOS mode or use a boot diskette and use the command line scanner:


Additional Windows ME/XP removal considerations

Users should not trust file icons, particularly when receiving files from others via P2P clients, IRC, email or other mediums where users can share files.

AVERT Recommended Updates :

* Office2000 Updates

* Malformed Word Document Could Enable Macro to Run Automatically (Information/Patch )

* scriptlet.typelib/Eyedog vulnerability patch

* Outlook as an email attachment security update

* Exchange 5.5 post SP3 Information Store Patch 5.5.2652.42 - this patch corrects detection issues with GroupShield

For a list of attachments blocked by the Outlook patch and a general FAQ, visit this link .
Additionally, Network Administrators can configure this update using an available tool - visit this link for more information .

It is very common for macro viruses to disable options within Office applications for example in Word, the macro protection warning commonly is disabled. After cleaning macro viruses, ensure that your previously set options are again enabled.