Fish is a virus that spreads to other computers by copying its code to other files or programs.
Fish prevents access from programs to websites of several companies related with security tools (antivirus programs, firewalls, etc.).
Fish redirects attempts to access web pages of certain banks to spoofed pages, with the aim of logging information entered by the user in these pages.
Fish redirects attempts to access several web pages to a specific IP address.
Fish 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.
Fish uses the following infection strategies:
- Resident: once it has been run, the virus goes memory resident and stops functions belonging to the operating system. Therefore, every time the operating system or an application tries to access any of these functions, the virus will activate and infect new files.
- 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.