Upon infection, ABC becomes memory-resident at the top of system memory but below the 640K DOS boundary and hooks interrupts 16 and 1C.
Altered, but not infected, COM or EXE files will have 4 to 30 bytes added to their length.
No text strings are visible within the viral code in infected EXE files, but the following text strings are encrypted within the initial copy of the ABC virus: ABC causes keystrokes on the compromised machine to be repeated.
It seems double-letter combinations trigger this behavior, e.g. "book" becomes "boook [sic]".
System hangs may also occur when some programs are executed, a likely side effect of ABC-induced corruption.