Brontok.A is a worm that spreads by copying itself, without infecting other files.
Brontok.A uses the following propagation or distribution methods:
Exploiting vulnerabilities with the intervention of the user: exploiting vulnerabilities in file formats or applications. To exploit them successfully it needs the intervention of the user: opening files, viewing malicious web pages, reading emails, etc.
Email: sending emails that include a copy of itself as an attachment. The computer is infected when the attachment is run.