Some e-mail worms, like the widespread Bagle-family, uses password-protected files in an attempt to fool antivirus scanners. F-Secure Anti-Virus provides methods that can be used to detect the presence of suspicious files inside encrypted archive files. These methods provide generic detection and work for all present and future worms that uses a similar technique.
Disinfection & Removal
These features are disabled by default due to the fact that they may have a negative impact on the scanning performance or block some legitimate attachments in mail traffic. This article describes how a user can enable these features and ensure that worms can't replicate using password-protected archives.
More information can be found from our Support pages: