BAT.Sys.a

This spyware is usually absolutely harmless, but in several situations it is still able to produce some damage. BAT.Sys.a copies itself to the AUTOEXEC.BAT on the floppy disk; that means this trojan is automatically executed when a computer is loaded from the infected floppy. BAT.Sys.a additionally infects the file SYS.COM in WINDOWSCOMMAND and renames it to SYS.OLD. This technique allows this trojan to be executed each time when the user calls SYS command.