Mydoom.M worm creates encrypted log files and sometimes sends them out instead of its own code due to a bug. As a result, the encryped data files are sent in a ZIP archive inside e-mails. The files have random (encrypted) content, they are about 1.1 or 1.2 kilobytes long. F-Secure Anti-Virus detects them as "I-Worm.Mydoom.m.log". Please delete messages and files that are detected as such by F-Secure Anti-Virus.
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 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.