In a few words...

This virus does not have a description.

The following symptoms may happen: after 22 minutes, the mouse Y axis will be inverted for 10s.

Details

• Replication: on any floppy when a get_bpb() is called, except if the virus signature is found (value 5 at 4th byte of the bootsector)
• Bootcode size: 308 bytes.
• Resident address: diskbuf.
• Start address: 0x40.
• Stealth address: 0x600.
• Attached vectors: hdv_bpb, vbl_queue.
• Reset resistance: Yes.
• TOS: All.

What's special ?

• A kind of rework of the Ghost virus, done differently. This kind to invert the mouse Y axis, commands are sent to the ACIA from a VBL queue routine. Works but fairly bigger and complicated.
• As commonly seen, it uses the undocumented resident routine to set up the vectors but from a set of addresses previously saved in 0x5e4-0xef8
• uses FLOCK to decide to show the symptoms or not, not clear why

How to trigger the symptoms? - Install the virus and reboot, check the hdv_bpb vector is set and also the Resident routine to $600 - Quit to GEM and run Tiny Tool accessory - Read memory address $5e0, set the byte to $FE and click Write - Wait a few seconds and the mouse will be inverted for 10s

Fun facts

• the description in the UVK book is not totally accurate:
• "Virus attaches itself to: Hdv_bpb, undocumented reset-resistant.": also tho vbl queue
• "Disks can be immunized against it: No": in fact yes if the signature is set in the OEM bytes

See the virus in action!