1. Rename attachments on the fly. Renattach is a small, efficient and surprisingly effective filter designed primarily to offer an additional level of safety to Windows users whose e-mails pass through a UNIX-like mail server. Many modern viruses are spread through e-mail, and renattach combats such viruses by filtering e-mail attachments based on file extension. In version 1.1.1, the MIME type is also renamed. The idea is to rename potentially dangerous attachments (executable ones) so that the user, or the user's poorly written e-mail software, does not accidentally execute the attachment. From Debian 3.0r0 APT