McAfee > Theat Center > Virus Detail Page

Overview

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.

Aliases

• Agena

• Agena.723

Characteristics

Agena.723 is a memory resident infector, file infecting virus. It infects .COM and .EXE files, including COMMAND.COM.

Upon infection, the Agena.723 virus becomes memory resident at the top of system memory but below the 640K DOS boundary. Interrupts 20 and 21 are hooked by Agena in memory.

Once the Agena.723 virus is memory resident, it infects .COM and .EXE files, as they are executed.

It is not known what Agena.723 does besides replicate.

Additional Comments:
The Agena virus was discovered in Spain in September, 1992. Agena is a memory resident infector of .COM and .EXE programs, including COMMAND.COM. When the first program infected with the Agena virus is executed, the Agena virus will install itself memory resident at the top of system memory but below the 640K DOS boundary. Total system and available free memory, as indicated by the DOS CHKDSK program, will have decreased by 1,296 bytes. Interrupts 20 and 21 will be hooked by Agena in memory. Once the Agena virus is memory resident, it will infect .COM and .EXE programs, including COMMAND.COM, when they are executed. Infected programs will have a file length increase of 723 to 738 bytes with the virus being located at the end of the file. The program's date and time in the DOS disk directory listing will not be altered. No text strings are visible within the viral code in infected programs. It is unknown what Agena may do besides replicate.

Symptoms

Total system and available free memory decreases by 1,024 bytes. Infected files have a file length increase of 723 to 738 bytes. The virus is located at the end of the file. The file's date and time in the DOS disk directory listing are not altered.

No text strings are visible within the viral code in infected files.

Method of Infection

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.

Removal

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.

Variants

Variants

• Agena

All Information

Overview -

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.

Aliases

• Agena

• Agena.723

Characteristics

Characteristics -

Agena.723 is a memory resident infector, file infecting virus. It infects .COM and .EXE files, including COMMAND.COM.

Upon infection, the Agena.723 virus becomes memory resident at the top of system memory but below the 640K DOS boundary. Interrupts 20 and 21 are hooked by Agena in memory.

Once the Agena.723 virus is memory resident, it infects .COM and .EXE files, as they are executed.

It is not known what Agena.723 does besides replicate.

Additional Comments:
The Agena virus was discovered in Spain in September, 1992. Agena is a memory resident infector of .COM and .EXE programs, including COMMAND.COM. When the first program infected with the Agena virus is executed, the Agena virus will install itself memory resident at the top of system memory but below the 640K DOS boundary. Total system and available free memory, as indicated by the DOS CHKDSK program, will have decreased by 1,296 bytes. Interrupts 20 and 21 will be hooked by Agena in memory. Once the Agena virus is memory resident, it will infect .COM and .EXE programs, including COMMAND.COM, when they are executed. Infected programs will have a file length increase of 723 to 738 bytes with the virus being located at the end of the file. The program's date and time in the DOS disk directory listing will not be altered. No text strings are visible within the viral code in infected programs. It is unknown what Agena may do besides replicate.

Symptoms

Symptoms -

Total system and available free memory decreases by 1,024 bytes. Infected files have a file length increase of 723 to 738 bytes. The virus is located at the end of the file. The file's date and time in the DOS disk directory listing are not altered.

No text strings are visible within the viral code in infected files.

Method of Infection

Method of Infection -

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.

Removal -

Removal -

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.

Variants

Variants -

• Agena