Attachments are files that are attached to an email or messenger service. They can be any file format, i.e. text files, graphic files, audio files and video files.
The attachment is often sent in a portable file format such as Portable Document Format( PDF), which allows it to be transferred between a wide variety of computers.
Various providers only support attachments that do not exceed a certain file size of about 10 MB. The file size of the attachment, together with the data rate, determines the transmission time. Large file attachments of 10 MB require about 3 minutes for transmission at an effective data transfer rate of500 kbit/s.
However, e-mail attachments are also a gateway for attackers who embed or attach their malware in the form of viruses, Trojans and spam to the attachments.