This article is from the Computer Viruses FAQ, by Nick FitzGerald n.fitzgerald@csc.canterbury.ac.nz with numerous contributions by others.
The Jerusalem virus and WordPerfect 4.2 program combination is an
example of a virus and program that cannot be completely disinfected by
an antivirus tool. In some cases such as this, the virus will destroy
code by overwriting it instead of appending itself to the file. The
only solution is to re-install the programs from clean (non-infected)
backups or distribution media (see D10 and E8).
 
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