Ufro
Description Ufro
It is not a dangerous memory resident encrypted boot virus. It hooks INT 13h and overwrites the MBR of the hard drive and boot sectors of the floppy disks. While infecting a disk the virus does not store the original contents of the boot/MBR sector. While loading from infected disk the virus in any case reads and passes the control to the first boot sector of the C: drive.
On 6th of any month the virus displays the message and halts the computer:
UFRO
IEE-1987
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ABCD.a
Description ABCD.a
It's a harmless boot virus. On loading from infected disk, it hooks INT 13h and writes itself into boot sectors of floppy disks. It infects the hard drive on loading from infected floppy. It uses the ID-word ABCDh.
Abola.2420
Description Abola.2420
This is a very dangerous memory resident parasitic virus. It writes itself to the end of EXE and to the beginning of COM files that are terminated (on INT 22h call). The virus stays memory resident only if the XMS driver is installed. While copying its resident code, the virus patches the XMS driver, hooks INT 2Fh and leaves its code in Upper Memory.
The virus utilizes a rather unusual way of accessing the files - during INT 2Fh calls, the virus scans memory blocks and patches INT 22h (Terminate) address in programs' PSP. When these programs are terminated, the virus will infect them.
On Tuesdays, the virus overwrites the disk sectors with the string:
AbolaAbolaAbolaAbolaAbola
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