Lebanese security forces recently detained an Iranian diplomat at Beirut’s airport carrying large amounts of cash, according to Israeli business daily Globes.

Hezbollah’s main source of funds, about 90%, is cash coming from Iran—close to $1 billion a year, according to Israeli security estimates. The rest comes from the drug trade and “charities” operated by the terror group.

One of the main challenges of Lebanon’s new president, Joseph Aoun, will be stopping that cash flow, according to Globes.