Well, we will have to come up with ideas how to defeat ISIS. Theoretically speaking, the only option requires everyone all over the world to come together and work against ISIS (including some of the world's biggest companies).
Social media giants should shut down accounts linked to ISIS, and set up a combined task force to hunt them down. This is how they try recruit, and I think the technology sector can help a lot more here. Data mining software can help, too. Whatever ISIS does, whether it's to do with financing their operations or their communication, it will leave a trace. Technology that helps here already exists (e.g. Palantir - a data mining company that was funded by the CIA, and whose software essentially led to the death of Osama bin Laden).
Given that there aren't many islamic banks, terrorists must be using global banks. There will be traces here. If the kind of tech companies I mention above could help analyze data from the banks, we might get further. This is Big Data, so should theoretically not break confidentiality clauses. And even if, things are flagged up, these banks actually have a duty of care to prevent money laundering, and should be able to intervene legally.
Adopting a no-nonsense approach is also required. Even we know from the news where ISIS is. Where their training camps are is probably not too much of a secret either. Stop filling pity for those who joined. Use long-range missile bombs with maximum efficiency.
If everyone in the developing world came together just for once, ISIS could be stomped out. Quite sure about that. Whatever tech they have, we should be able to beat it.