MS-DOS

Jerusalem.B is a resident virus that infects files with an EXE, SYS and COM extension. This virus is activated when the date on the system clock is Friday 13^th and it deletes all files run on the computer.

Jerusalem.B increases the size of infected files. The size of a file increases every time the infected file is run. It can also cause the computer to slow down.

Jerusalem.B does not use any specific means to spread. It can reach computers through the usual means used by viruses: Internet downloads, floppy disks, FTP, etc.

Jerusalem.B is difficult to identify, as it does not display any messages or warnings that indicate that it has infected a computer.