Python Boto Code to update your EC2 instance's Security Group to be in sync with your changing Public IP

EC2-SG-PublicIP-Fixer

# Python Boto Script to Update the EC2 security group to make the instance 
# to be open to your public IP although ISP change
# Can be automated in CRON everyday

import boto
import urllib2

def get_public_ip():
    ext_ip = urllib2.urlopen("http://curlmyip.com").read()
    return ext_ip.strip()

sg_name = '<your security group name>' #enter your Security Group's NAME

ec2 = boto.connect_ec2()
sg = ec2.get_all_security_groups(groupnames=sg_name)
sg = sg[0]

#remove existing 22 SSH rules - old CIDR IP
for rule in sg.rules:
    if str(rule.from_port) == '22':
        ec2.revoke_security_group(group_name=sg_name,
                                  ip_protocol='tcp',
                                  from_port='22',
                                  to_port='22',
                                  cidr_ip=rule.grants[0])

#Authorize today's Public IP
ec2.authorize_security_group(group_name=sg_name,
                             ip_protocol='tcp',
                             from_port='22',
                             to_port='22',
                             cidr_ip=get_public_ip()+"/32")