<?xml version="1.0"?>
<config>
    <modules>
        <Naveed_Abbas>
            <active>true</active>
            <codePool>local</codePool>
        </Naveed_Abbas>
    </modules>
</config>

<?xml version="1.0"?>
<config>
    <modules>
        <Naveed_Abbas>
            <version>0.1.0</version>
        </Naveed_Abbas>
    </modules>
    <global>
        <models>
            <naveed_abbas>
                <class>Naveed_Abbas_Model</class>
                <resourceModel>naveed_abbas_resource</resourceModel>
            </naveed_abbas>
            <naveed_abbas_resource>
                <class>Naveed_Abbas_Model_Resource</class>
            </naveed_abbas_resource>
            <payment>
                <rewrite>
                    <method_cc>Naveed_Abbas_Model_Payment_Method_Cc</method_cc>
                </rewrite>
            </payment>
        </models>
        <blocks>
            <naveed_abbas>
                <class>Naveed_Abbas_Block</class>
            </naveed_abbas>
        </blocks>
        <helpers>
            <naveed_abbas>
                <class>Naveed_Abbas_Helper</class>
            </naveed_abbas>
        </helpers>
    </global>
</config>

<?php

class Naveed_Abbas_Model_Payment_Method_Cc extends Mage_Payment_Model_Method_Cc {
 // overwrite your method here
 public function validate()
 {...}
}

<models>
    <your_module>
        <class>Your_Module_Model</class>
    </your_module>
    <payment>
        <rewrite>
            <method_cc>Your_Module_Model_Method_Cc</method_cc>
        </rewrite>
    </payment>
</models>