In simplistic terms the Scud is a 1950s or 60s version of the old German V2. The USSR built a ton of them in many variations and foisted them off on their client states during the Cold War. Since then the owners who have no use for them have happily traded them about to those who want them. Generally they have to upgraded with new guidance systems if they are to hit anything, and often the propulsions systems must be rebuilt, or the fuel replaced if a solid fuel model. The payload can be about anything. A HE charge, bomblets, chemicals, ground up Plutonium, a flag with 'BANG' printed on it. Even if the warhead is loaded with packing bubble wrap these things are dangerous as you have several thousand Kg of metal falling from the sky, with whatever flamable and toxic fuel residue there is. The Scuds of Desert Shield were launched by the dozens & did little damage. Realative to the cost to the Iraqi government they were a failure, except the panic over them constituted some sort of propaganda gain.

To answer the last question, truck bombs are cheaper, easier for attacks like you describe, and far more accurate and effective than the Scuds.

Whats the difference between a scud and a tomahawk cruise missle? Could you launch a cruise missle from a truck the way you can scuds? Is the only advantage to a cruise missle that they are more accurate? (aside from launching them from ships/subs)

The Scud is a ballistic missile, not a cruise missile like the Tomahawk. A ballistic miisle works by flying a ballistic arc from the launch point to the target, it launches high into the atomosphere, the fule is cut off, and then it falls and hopefully hits is target, old Scuds had radiocontorled fuel cut off more morden ones had internal guidence. Iraqi scuds had half the warhead taken out to increase range, but this distablised the flight pattern so it was really inaccurate. Flight is not sustained as with a crusie missile which uses a boost rocket motor for lift off, then flight is sustained with a mini jet engine. Crusie missile also fly close to the ground. And yes the US did develop a Ground launch system for the Tomahawk but I believe it has been removed from service, not sure thoguh.

Oh and I think North Kores attached Scud launchers to flat deck cargo ships, I have no idea how affective they would be.

As with the original V2 ballisitc missles are usually equipped with gyroscopic based guidance systems. But the Scuds & many similar missles are often copies of the 1940s German technology. As they fall on the downside of the trajectory the speed is extreme, often above the sound barrier (which causes a unstable missle to disintigrate). The old style guidance systems cant provide pinpoint accuracy in this context. Of course there are much better guidance systems installed on the best US and Soviet ballisitc missles, but these are not availalbe to the average missle buyer. Crusie missles travel at realatively low speeds an have larger aircraft style wings. These two factors allow a much more precise control.

Ground Launched Cruise Missiles were operated by USAF from a couple of bases in UK (also Italy?) in the 1980s.