Possible Clues:

• Hard worker in Paris, say
• Computer threat
• Vergers from Treguier love month in Paris?
• Native like Helen
• Kind of virus in computers
• Enemy within a month or two's heading back to the front
• Hector or Paris
• Seen in bistro, January's 'most industrious worker'
• Harmful program
• Hard worker making veiled threat to PC?