F-Secure Virus Descriptions : Finnish Sprayer

NAME:	Finnish Sprayer
ORIGIN:	Finland
TYPE:	Resident Boot sectors Stealth

Finnish Sprayer was found in Finland in November 1993, and it quickly became very widespread in the southern parts of Finland.

The virus will only infect hard drives when an attempt to boot from an infected diskette is made. Once the virus has infected the hard drive, all non-protected floppies used in the machine will be infected. The virus contains the following unencrypted text: "Tks to B.B, Z-VirX ..... [Aija]".

Finnish Sprayer is two sectors long, and it stores the original boot sector and it's own code to the last sectors of the active partition.

The virus activates on the 25th of March. At this date it will overwrite most sectors of the active partition with random data, change the screen background to grey, and display the following text:

 FINNISH_SPRAYER.1. Send your painting +358-0-xxxxxxx (FAX), [Aija]

This text is not visible in the virus code, since it has been encrypted with a XOR 50h operation.

Finnish Sprayer will not infect the hard disk if the active partitions file system is not DOS. This means that PC's running for example OS/2, DR-DOS with HD password protection, Windows NT or some UNIX variant will not be infected.

Virus uses stealth routines, so it cannot be found from hard disks MBR when it is active in memory. F-Secure anti-virus products will detect if Finnish Sprayer is resident, and will advise you to boot from a clean diskette.

[Analysis: Mikko Hypponen, F-Secure]