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This is probably the best explanation of how the files and software were suddenly erased. A virus is a program that alters the way another computer operates. Viruses can damage programs, delete files or reformat the hard disk. A backdoor in a computer system is a method of bypassing normal authentication or securing remote access to a computer, while attempting to remain hidden from casual inspection.
The programmer was more than likely denied access to the computer center.
In these circumstances, it is not likely that there was collusion.
The passwords were disabled, so the programmer would not know the new passwords.