Thay have obviosly claimed your porch as their territory.The cats are most likely stray/wild, a TRUE feral animal is not afraid of humans and will attack them as an intruder in their territory. It is best to start trying to get them used to humans as young as possible if you want them to be "pets". I did this with a young kitten who was a wild stray, he was near death when found in the parking lot and paralyzed in his hind end. It had a good ending, the pararlysis was only temporary and he got better, he preferred a quiet houshold, preferably with other cats, he had to be an indoor cat only due to some lasting knee damage in his hind leg. Your best bet would to get a live trap and get them checked out by a vet and move them indoor for awhile if you want them human friendly quickly, or just get them fixed to keep the population down.

Since your place is your territory they will chase other cats away. The University in Austin Texas has a stable wild cat population, they feed them and keep them up to date on their shots, all are fixed of course, and it keeps the stray population down to a minimum since they protect their territory. You could also try putting out a litter box for them? Make sure they don't "belong" to some neighbors who are letting them be "free and natural", I have run into those people before who don't get them shots or anything, "they can catch their own food right? they did well before humans interfered with them". People like that make me mad.