Fosforo is a virus that spreads to other computers by copying its code to other files or programs.
Fosforo does not spread automatically using its own means. It needs an attacking user's intervention in order to reach the affected computer. The means of transmission used include, among others, floppy disks, CD-ROMs, email messages with attached files, Internet downloads, FTP, IRC channels, peer-to-peer (P2P) file sharing networks, etc.
Fosforo uses the following infection strategies:
- Stealth: when the virus is memory resident, it hides the modifications made to the boot sectors or files it has infected. These modifications are: changes in size, date, attributes, etc.
- Polymorphic: it encrypts itself in a different way with each infection it carries out. In order to do this, it uses different keys and operations. As a result, the virus has different characteristics in each new infection, which makes it difficult for antivirus pro-grams to detect this virus.
- Encrypted: it encrypts its code in order to make it difficult to detect. In order to carry out its infection, the virus decrypts itself and, once infection has been carried out, it encrypts itself again.