sudden dog aggression

Question
I have 5 Maltese ranging from 1 to 11 yrs of age.  Recently my 2 year old male has  been attacking the the other 2 males, one of which is his father. They now hide under the bed in fear of a sudden attack. The females are never attacked. One of the females was spade and the other is her puppy.  How do i stop this behavour and why suddenly has this started?

Answer
Is he injuring them? Often a toothy display looks dangerous and scary but is understood by the dogs. You don't say in what situations he is "attacking" them. Is it over food? the girls? You? Are there space issues (five dogs in a very small area?) Are the males all intact? could the female be coming in heat? Lots of different variables there, which you'd have to think of to come up with why this is happening and what to do about it.
At two years old, a dog is coming into social maturity, and may be looking for the top position in the family "pack" That is about the age you would expect the dog to make his move. While Malteses aren't known for being dog aggressive, it can be very difficult to have multiple males (especially intact, or some intact/some not) kept together without disagreements. So the behavior may less abnormal than the expectation that they can all live peacefully without any posturing or displays.
What to do about it? You can play rotat0dog, running the feisty boy with the girls and the two peacable boys together. You can get professional in-person help. (and unless you can keep a really detailed record of exactly what is happening - sometimes the provoking dog isn't who you think it is) that would be the best way to answer some of your questions about why. You can consider snipping them to get rid of the testosterone edge (though that may not solve the issue). You can start a daily training plan - especially with the feisty boy, using NILIF (http://k9deb.com/nilif.htm), clear boundaries and fair, clear rules to establish yourself as the benevolent leader of the household, so he doesn't feel as much need to step up and make rules for the other dogs. Also, I know we get dogs because we love to love on them. But excessive cuddling and spoiling (not saying that you are - just that it isn't uncommon, especially with lap dogs) sends a clear message to the dog that he is the little king of the universe. So watch any such tendencies. Sandy Case, MEd CPDT www.positivelycanine.com