This is a typical stealth boot sector virus, which beeps and displays this text after every 15 infected floppies:
ystanbulCCC was here! He he
Otherwise the virus just spreads.
IstanbulCCC was reported to be in the wild in the UK in April 1996.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
More information on scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for more information.
Technical Details:Peter Szor, F-Secure, 1996