In the new standard IFS 6 (valid as of 1st of July, 2012) you will find the category of so called "Food Defense" measures at your facility and at the facilities of your supplier's.
What is this about?
Food Defense means: "all measures taken to prevent malevolent manipulation of your production and supply chain/s".
If your customer requests you to deliver a statement about the subject, you could describe the protective and security measures you implemented in the following areas of your production facility/facilities:
External areas: Access controls, emergency systems, fences etc.
Internal area: Control and security systems, access controls, handling of dangeorus goods
Incoming and outgoing goods: Control of driving personnel, agreements with logistics service providers, handling of returned goods
You will find a detailed guide on the issue here as a PDF on the IFS web site. More on the new requirements of IFS 6 here.