[3] Once triggered, the virus not only deletes any program run that day,[4] but also infects .EXE files repeatedly until they grow too large for the computer.
The virus contains code that enters a processing loop each time the processor's timer tick is activated.
Symptoms also include spontaneous disconnection of workstations from networks and creation of large printer spooling files.
Disconnections occur since Jerusalem uses the 'interrupt 21h' low-level DOS functions that Novell NetWare and other networking implementations required to hook into the file system.
Jerusalem was initially very common (for a virus of the day) and spawned a large number of variants.