The Economist has an article on the continued growth of the tunnels in the Gaza strip.

Once a secretive and dangerous industry, smuggling has become open, even respectable. As recently as last year, Israeli jets would destroy any sites suspected of housing tunnels, but now the smugglers are working in clear view of Egyptian border posts and Israeli surveillance.

As Havocscope earlier mentioned, smuggling in the Gaza Strip is a profitable enterprise, with various goods being provided through the tunnels.

However, the tunnels are used for much more than munitions. Nasser, a pharmacist in Rafah, says that he receives regular visits from smugglers offering to supply him with medicine bought in Egypt. While he does buy dried milk and drugs, his most popular import is generic Viagra, made in India, which he sells for 75 cents a tablet.

Israel declared Gaza a “hostile entity” last month and promised more restrictions. But as it tightens them and poverty rises, smuggling becomes a more attractive risk. Abu Adnan, a 21-year-old, said he had been working in Rafah’s tunnels since he was 14 and can make around $7,000 per shipment. He has smuggled weapons, people and cash, but now the most popular import is cigarettes which Israel has stopped.

The smugglers use technology and equipment that anyone can purchase off the shelf of a hardware store, and also uses Goggle Maps to plot out the tunnel route.

The smugglers are almost always private entrepreneurs. They first select a piece of land close to the border wall and then dig a large hole with a mechanical digger. They then enclose an area of dozens of square metres and start digging, filling the first hole with the earth from the tunnel. They can map the length and direction of the tunnel accurately using satellite pictures from Google Earth.