Following on from the terrorism events on 11 September 2001 in the U.S., the International Maritime Organization (IMO) agreed to develop security measures applicable to ships and port facilities. These security measures have been included as amendments to the Safety of Life at Sea (SOLAS) Convention, 1974 as amended. It was in force by all member nations after July 1, 2004. It is known as the International Ship and Port Facility Security (ISPS) Code.

The objectives of the ISPS Code are to:
• establish an international framework involving co-operation between contracting governments, government agencies, local administrations and the shipping and port industries to detect/assess security threats and take preventive measures against security incidents affecting ships or port facilities used in international trade;
• to establish the respective roles and responsibilities of all these parties concerned, at the national and international level, for ensuring maritime security;
• to ensure the early and efficient collation and exchange of security-related information;
• to provide a methodology for security assessments so as to have in place plans and procedures to react to changing security levels; and
• to ensure confidence that adequate and proportionate maritime security measures are in place.

Each ship shall have her ISPS Security Plan which contains the action plans against 3 different security levels, security assessment, record keeping, names of the ship and company security officers, training of security officers as well as shipboard personnel, and a schedule of the periodic drill. Furthermore, each ship is subject to the ISPS verifications and shall possess a valid International ship Security Certificate on board the ship. From the port facility side, each contracting government shall mandate its port facility operator to formulate an action plan upon each of its own security levels including its emergency evacuation plan, carry out its security assessment by a recognized security organization or a certified person, maintain an up-to-date facility security plan, designate a Chief Facility Officer in charge of security, identify the facility security risks, prevent unauthorized access to ships, port facilities and its restricted areas, and provide training not only to the security officers but also to all facility personnel.

The ISPS Code contains three security levels.
• Security Level 1, normal; the level at which ships and port facilities normally operate.
• Security Level 2, heightened; the level applying for as long as there is a heightened risk of a security incident.
• Security Level 3, exceptional; the level applying for the period of time when there is a probable or imminent risk of a security incident.