I've always looked at it that way. The international terrorist "community" is like a marketplace where there's a demand for certain goods (guns, bombs, drugs, etc.) and expertise (passport forgery, demolitions, and so on), and there's a limited number of suppliers, so there are bound to be links. Also many present terrorist groups are networked with old roots in either the Comintern network or the Axis Anti-Kommintern network. To take a notable example, Carlos is still out there, and he's made some statements about wanting to network with Al Qaeda and other terrorist groups recently.