Virus Database

Joshi.a

Description Joshi.a

These are dangerous stealth viruses. They infect floppy disks Boot-sectors and hard disk MBR during an access to them (INT 13h, ah=2,3,4,0Ah,0Bh). The viruses include two parts - the first part contains the body of the virus and is placed onto the boot sector (or MBR) of the disk, the second part contains the original first sector of the infected disk and the other eight sectors of the virus, and occupies the 40th or 80th track of the floppy disk (the virus uses nonstandard format); on the hard disks the second part of the virus body begins from the second sector of the starting track. The viruses can destroy FAT when they save their own copy on the disk.
The viruses hook INT 21h. Just after starting (rebooting of the system) they permanently check the interrupt vector 21h, and if it is changed the viruses read the new value of the vector. The viruses hook INT 9h (keyboard). When the ALT-CTRL-DEL keys are used to boot the system, the viruses will emulate rebooting: clear the screen and so on. The viruses will stay resident even if you boot the system from a clean and write-protected floppy disk.
On the 5th of January the viruses will display the message "Type `Happy Birthday, Joshi'!" and will wait for the entering "Happy Birthday, Joshi!" from the keyboard. The viruses hook the INT 8, 9, 13h, 21h.

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Ka.863

Description Ka.863

It is a harmless memory resident parasitic partly encrypted virus. It hooks INT 21h and writes itself to the end of .EXE files that are executed. It contains the text string:
KA

Kaczor.4444.a

Description Kaczor.4444.a

It is not a dangerous memory resident polymorphic stealth multipartite virus. It traces and hooks INT 13h, 21h and writes itself to the MBR of the hard drive and to EXE files that are accessed on the floppy disks. On accessing to the infected files on the hard drive the virus disinfects them.
While installing memory resident from infected hard drive the virus also temporary hooks INT 12h, 1Ch. On DOS loading it cuts the block of system memory, hooks INT 13h, 21h and resets INT 12h, 1Ch.
That virus is encrypted in memory as well as in the files. The INT 13h, 21h handlers decrypt the code of subroutines before processing them, and then encrypt before return to the original interrupt handlers.
On loading if the keyboard buffer contains the word "kaczor" the virus disinfects MBR and displays:
Zrobione.

If the keyboard buffer contains the word "test", the virus displays the message:
Wersjaall.......
Kodowanie.......
Licznik HD......

and adds corresponding numbers to the ends of these strings.
On March, 3rd the virus hooks INT 8 (timer) and "shakes" the screen.

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