| Alias: | --- |
| Strain: | --- |
| detected when: | May 1988 |
| where: | Amherst (USA) |
| Classification: | Boot sector virus |
| Length: | 681 Bytes |
Preconditions | |
| Operating System(s): | Atari TOS |
| Version/Release: | ROM TOS from 02.06.1986; in other versions, no action is per |
| Computer model(s): | All Atari ST |
| Caroname: | Blot |
Attributes | |
| Easy identification: | In memory at Phystop +34 and in the boot sector at the same offset, the following bytes can be found: $0206198600FC0018 |
Type of Infection: | Boot sector of drive A. |
| Infection Technique: | |
| Infection Trigger: | Usage of drive A. |
| Storage Media affected: | Drive A. |
| Interrupts hooked: | 200 Hz interrupt , Bios Parameter Vector. Critical Error Handler at infection time. Phystop is decremented by 1 KByte. |
| Stealth: | |
| Tunneling/Selfprot: | |
| Oligo/Polymorphism: | |
| Encoding Method: | |
| Damage: | The screen is blacked out from bottom to middle and from top to middle at same time. |
| Damage Trigger: | Virus is about 3 hours in Ram. (Depends on value of 200 Hz timer). |
| Particularities: | Only boot sectors that aren't executable are in- fected. |
| Similarities: | The general concept of the virus is similar to the 'Screen'-Virus |
Agents | |
| Countermeasures: | Make sure that the virus is not in memory. Search bootsector for the string mentioned above. Modify last byte in boot sector to another value. |
| Standard means: | Clear all bytes in bootsector (sector 0) beginning at offset 30 (dec) and clear all bytes in sector 5. |
Acknowledgements | |
| Location: | Virus Test Center, University of Hamburg FRG |
| Classification by: | |
| Documentation by: | Ralf Stegen |
| Date: | 5-June-1990 |
| Information Source: | George R. Woodside |
(c) 1996 Virus-Test-Center, University of Hamburg