Israel's Arrow ABM (anti-ballistic missile) program is a two billion dollar collaboration between Israel and the United States. But Israel is upset when they found out that the American firm, IBM, had Egyptian software engineers work on upgrades to the Arrow software. Israeli security officials feared that the Egyptians engineers might have been contacted by Egyptian military intelligence and made to insert a "Trojan Horse" program in the software. This would have caused the Arrow missile to fail under certain conditions (like intercepting missiles coming from the south, where Egypt is.) IBM denied that this was possible, but removed the Egyptian engineers from work on the Arrow software. IBM maintains software development operations in Israel and Egypt (and dozens of other countries) and regularly had the Egyptian and Israeli engineers work together on projects for Middle Eastern clients.