Freeze Virus (31-January-1991)
Entry...............: "Freeze" Virus
Alias...............: ---
Strain..............: ---
Detected when.......: October 1988
         where......: Helmond (Netherlands)
Clssification.......: System (bootsector) virus, overwriting
Length of virus.....: 512 Bytes
------------------------Preconditions---------------------------------
Operating System(s).: Atari TOS
Version\Release.....: All versions
Computer models.....: All Atari ST
-------------------------Attributes-----------------------------------
Easy identification.: The words : $487A,$0010 can be found in the boot
                         sector at Positon $100, or in memory at 
                         :phystop-$300+$100 (all: hex).
Type of infection...: Executable bootsectors are not infected.
Infection Trigger...: Execution of BIOS disk functions.
Media affected......: The virus infects drive A and B. 
Interrupts hooked...: Timer interrupt installed for damage; hdv_bpb 
                         changed to infect bootsector of new disk.
Damage..............: Every second the timer-routine increases a delay 
                         counter by 1 and then counting it down to 
                         zero; this will slowdown the system.
Damage trigger......: When the virus is booted.
Particularities.....: If harddisk SH204 is connected, the virus 
                         causes an address error and will not be 
                         installed.
Similarities........: The same installation routine as MAD virus; only 
                         different damage action and damage trigger. 
----------------------------------------------------------------------
Countermeasures.....: Make sure that virus is not in memory; modify
                         last byte in bootsector to another value.
Standard means......: Clear all bytes in bootsector beginning at
                         offset 30 (decimal).
-----------------------Acknowledgements-------------------------------
Location............: Virus Test Center, University of Hamburg FRG
Classification by...: Thomas Piehl
Documentation by....: George R. Woodside
Date................: 31-January-1991

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