Immediately rise to a superior physical position.
100% completely and utterly ignore your Maltipoo. This must be done to such a degree that your dog begins to question if he's been banished from the 'pack'. No eye contact, no speaking (be careful speaking to other household members, so that there's no confusion), no interaction at all. Do not respond to barking or jumping.
If your Maltipoo does hang onto your leg or keeps jumping up on you, you can skip to step 8, below.
Wait it out. It takes dogs a while to realize that they are being ignored. And it takes puppies even longer. When your Maltipoo starts to whine, paces, or otherwise seems troubled, this is your clue that he's noticed.
At the very least, this should be done for 10 minutes.
Once this session is complete, return to the exact same positioning that you and your dog were in when the aggression happened.
If he nips or growls again, repeat your response again.
If he behaves nicely, offer praise and the special treat that we've mentioned under 'What You Need
If the aggression continues, repeat the ignoring 2 times total. Upon the 4th aggressive action, it will be time to step things up and give a time-out in the designated area.
This does not need to be a barren spot. If you're using this area as we recommend, it will have your Maltipoo's bed, water bowl, pee pads, and a nice collection of toys. And that is fine. The idea is not to make your dog uncomfortable. Rather, it is to give temporary banishment.
Also, per guidelines of having the right set-up, this should be in a family area such as the living room or kitchen. You do not want this to be in some area out of the way, because if so, your Maltipoo won't realize that he's being ignored.
During the time-out the dog should be 100% completely ignored as explain in step 3 above.
And, as with step 4 above, you must wait it out. In the designated area, it can take 20 to 30 minutes for your puppy or dog to notice.