Last week's terror attack in Sinai, which claimed the lives of 16 Egyptian soldiers, prompted the authorities in Cairo to clamp down on the smuggling tunnels connecting Egyptian Rafah and the Gaza Strip. Dozens of bulldozers arrived at the Egyptian side of the Philadelphi Route and began demolishing tunnels. On the other side, Hamas closed the tunnel entrances, at least for the time being.

For around 70,000 Palestinians whose livelihoods depend on the tunnels, it is a severe blow.

Ibrahim, a Rafah resident, is worried. For the past four years he has owned a tunnel used for transferring merchandise. Hamas' decision to shut the tunnels on the Palestinian side has seen his source of income collapse. "They closed everything after the attack. Three days ago they let open them again for 24 hours, in order to let our goods pass through, but then they told us they will be closed again," he said in a phone call from Rafah.

The precise number of tunnels is unknown. Palestinian and Arab media estimate there are 400 tunnels, while Ibrahim believes the actual number is closer to 500. A senior Egyptian official told Haaretz he estimates that some 1,200 entrances exist on the Palestinian side, but they serve no more than 350 tunnels. This means brisk business.

"There are 30 workers or more in each tunnel," Ibrahim says. "Every worker earns around NIS 100 a day. How will their families survive?"

Ibrahim used to work as a truck driver, transporting merchandise from the tunnels to the Gaza markets. Four years ago he decided to open a tunnel of his own, and needed no formal approval to do so. But things have changed.

"Today the situation is different," he says. "You have to receive approval from the 'tunnels committee.'"

The "tunnles committee" is comprised of Hamas representatives, who supervise activities in the tunnels and decide who is or isn't eligible to open a tunnel, which can be a very profitable business. Based on the permits issued by Hamas officials, committee heads have been accused of favoritism in granting permits and accepting bribes.

Is every tunnel supervised? Are there people who monitor you at the tunnels?

Ibrahim: "Certainly. There is a Hamas policeman or committee member at every entrance. They check everything that goes through, and verify that nothing illegal  - like alcohol, drugs or cigarettes - is smuggled. For example, it is forbidden to smuggle weapons. Anyone caught smuggling weapons will have his tunnel shut down. But these people are also responsible for weighing all commodities entering Gaza."

All merchandise is weighed?

"Yes, otherwise it would be impossible to figure how much tax needs to be paid. The supervisor inspects the merchandise, weighs it, and we pay taxes to the committee. For example, NIS 10 for every ton of cement. NIS 15 for every ton of gravel. My tunnel is used for various merchandise, especially construction materials, but also food. There were periods when there was a demand for Coca-Cola, or clothes. We call the Egyptian family which owns the [other] entrance to my tunnel and ask for certain goods according to the demand in Gaza. And, of course, there are also cars."

According to the Egyptian daily Al-Ahram, 13,000 cars came through the tunnels in 2011. Following Egyptian complaints that some of those cars were stolen, Hamas agreed that only brand-new cars could be transported into Gaza. Ibrahim and Abu Amar, another tunnel owner, claim that Hamas is in complete control of every person or commodity going through the tunnels - a fact that led Egyptian intelligence to accuse Hamas of turning a blind eye to global jihadists entering Sinai from Gaza. Still, sources in Gaza claim that there are other tunnels, east of the Rafah crossing, that aren't under Hamas control. These, allegedly are where the illegal goods, and the human beings, are smuggled.

Ibrahim adds that the cost of constructing a tunnel is about $70,000, and the total income from all tunnels can reach NIS 700,000 a day.

What will you do if the tunnels are closed permanently? Is that possible?

"Of course, if the Rafah crossing will be used to transport goods we won't need the tunnels. And I'll simply return to my truck," Ibrahim says.

Hamas' control of the tunnels yields some 10-15 percent of the movement's revenues. It also allows its officials to leave and enter the Strip. Meanwhile, the Egyptian authorities are focusing on demolishing the tunnels east of the Rafah crossing (those not directly controlled by Hamas ).

One can assume that a quiet understanding will eventually keep the Hamas tunnels  operating, one that takes into account Egypt's security demands and Hamas' financial needs.