Before you can log in to an instance, you must authorize access to that instance. This done by configuring a security group for that instance.
A security group is a set of networking rules applied to instances associated with a group. When you first create an instance, it is assigned to a default security group that denies incoming network traffic from all sources. To allow login and usage of a new instance, you must authorize network access to the default security group with the euca-authorize command.
To authorize a security group, use euca-authorize with the name of the security group, and the options of the network rules you want to apply.
Use the following command to grant unlimited network access using SSH (TCP, port 22) and VNC (TCP, ports 5900 to 5910) to the security group
euca-authorize -P tcp -p 22 -s 0.0.0.0/0 default euca-authorize -P tcp -p 5900-5910 -s 0.0.0.0/0 default