Bolzano infects Win32 EXE files. There are several variants.
Bolzano.A, B and C infect EXE files in traditional manner, while Bolzano.D uses inserting technique to infect EXE files.
Under Windows NT, Bolzano modifies NTOSKRNL.EXE so that any user has the rights to modify any file on NTFS volumes, regardless of their real user rights.
Bolzano is not common in the wild.
[By Mikko Hypponen, based on information from Peter Szor, 1997]