There are dangerous memory resident boot viruses. They hook INT 9, 13h and infect the floppy disks boot sectors that are accessed (INT 13h, ah=2,3,4,5). The viruses do not check the disks when place their second parts on a disk, so they can destroy some information at the 40th track. On a warm reboot they display their name "Den Zuk" in big letters (graphics video mode). The viruses replace the label of the infected disk with "Y_C_1_ E_R_P". They have not destructive functions, but they are dangerous because of the possibility to erase information at the 40th track on the infected disk. The viruses contain the text: Welcome to the C l u b --The HackerS-- Hackin' All The Time The HackerS