When it comes to aggressiveness in a dog this is a very serious problem. There are new laws that state dog's owner can be charged and the dog put down if the dog bites someone. Of course with some serious dog training our dog can learn to enjoy people not turn on them.
There are lots of reasons why dogs are or become aggressive. Maybe the dog feels his territory is being compromised, or he feels threatened. A lot of aggression comes from lack of confidence and insecurity. Simple obedience will not solve your dog's aggressive problems only some serious dog training will do the trick. Aggressiveness doesn't just mean biting; it means barking and lunging at people as well. This type of behaviour needs to be addressed as soon as possible to prevent anything serious from happening to someone or another dog.
Your vet can recommend you how to go about finding someone who can work with aggressive dogs. Training aggressive dogs is a speciality and unfortunately could cost you a fair amount of money, but the end result is well worth it and you don't have to worry about losing your dog. Most obedience and training schools wont take aggressive dogs as most of the places run classes with other members and won't let them be endangered. The best thing you can do is to take him to a proper dog school. Look in your yellow pages for one.
Always check the techniques used by schools on how they train aggressive dogs as training an aggressive dog can be dangerous some places may use out of date methods which could be harmful to your dog, although this isn't always the case it is always better to be safe than sorry. I wish I could say it was easy to train your do not to be aggressive but it isn't.
At the end of the day what counts is that your dog stops attacking and he starts loving. An aggressive dog can halter the relationship that you have with him therefore you and your dog aren't having the best time together as you are always worried about him biting you, other people or other dogs. I recommend that you do what it takes to get the problem sorted!