The infiltration by ISIS fighters is probably via Libya where US and its allies have a very strong hold thanks to Clinton. The handlers of ISIS are in Libya, Israel and Europe. There is hundreds of Kms border between Libya and Egypt which is mostly uncontrolled. It is very easy for the assets to use the land route, or use the uncontrolled sea routes to Egypt. Once these assets are inside Egypt, they can go anywhere they want. And that is why destabilisation of Egypt can become huge in the coming months.
