The bad code is divided into small pieces and is distributed in the whole file by some code-generator.
This technique makes analysis and detection difficult. What is the first thing the common user sees before running some file? The icon is code-generated as well as the whole file.
It's interesting to see bad-guys producing nice art.
And here inter alia can be seen the mathematical skill of the bad-guys.
As Swizzor evolves and each generation becomes harder to detect, the icon becomes more sophisticated too.
©Brain was the name of this virus, it infected the MS-DOS FAT boot sector and it was harmless.
This MBR rootkit just promoted their company with following text: Welcome to the Dungeon © 1986 Basit * Amjad (pvt) Ltd. We would reach 3 millions of detections in our virus database (VPS) this week, but ...
Easier way how to run attacker's code on victim computer is to convince users to download it voluntarily. It's based on a huge distribution network and is made by highly skilled bad-guys.