In January, the Congressional Research Service released a report on the threat of maritime terrorism.
While noting that "fewer than 1% of all global terrorist attacks since 1997 have involved maritime targets," the report discusses a few of the particular threats. It's an exercise in threat recognition.
The CRS notes that there are particular challenges to launching a maritime attack:
One U.S. naval analyst has identified a number of specific challenges for terrorists in the maritime environment:
- Maritime targets are relatively more scarce than land targets;
- Surveillance at sea offers less cover and concealment than surveillance on land;
- Tides, currents, wind, sea state, visibility, and proximity to land must all be factored into a maritime terror operation;
- Maritime terror operations may require skills that are not quickly or easily acquired such as special training in navigation, coastal piloting, and ship handling;
- Testing weapons and practicing attack techniques, hallmarks of Al Qaeda’s typically meticulous preparation, are harder and more difficult to conceal at sea than on land;
- The generally singular nature of maritime targets, the low probability of damage and casualties secondary to the intended target, and the problems associated with filming attacks at sea for terrorist publicity may also reduce the desirability of maritime targets.
Despite these difficulties, al Qaeda and other terrorists have chosen maritime targets in the past, including the USS Cole bombing in 2000, the attack on the French oil tanker Limburg in 2002, and the 2004 attack on the Philippine Superferry 14.
A maritime attack does not need to cause many human casualties to have an effect:
If economic loss is the primary objective, terrorists may seek to carry out different types of attacks, with potentially few human casualties but significant impacts to critical infrastructure or commerce. The Limburg bombing may have been an attack of this type, threatening to disrupt the global oil trade and causing considerable consternation among tanker operators. Although the bombing killed only one member of the Limburg’s crew, it caused insurance rates among Yemeni shippers to rise 300% and reduced Yemeni port shipping volumes by 50% in the month after the attack.
The report comments on the relative risks of different types of maritime attacks, starting with the nuclear "bomb in a box" (i.e., shipping container) scenario:
Expert estimates of the probability of terrorists obtaining a nuclear device have ranged from 50% to less than 1%. Among other challenges to obtaining such a device, experts believe it unlikely that countries with nuclear weapons or materials would knowingly supply them to a terrorist group. It also may be technically difficult to successfully detonate such a nuclear device. North Korea experienced technical failures in conducting its 2006 nuclear weapons test, and this test took place under highly controlled conditions. Attempting to detonate a nuclear device in a maritime terror attack could pose even greater operational challenges.
The risk of a "dirty bomb" attack may be higher, especially if the primary objective is economic damage, though there are skeptics:
Terrorist attacks on U.S. ports with radiological dispersion devices (“dirty” bombs) is also considered among the gravest maritime terrorism scenarios. A 2003 simulation of a series of such attacks concluded that they “could cripple global trade and have a devastating impact on the nation’s economy.” Many terrorism analysts view such a dirty bomb attack as relatively likely.
Scientists have long questioned whether terrorists could actually build a dirty bomb with catastrophic potential since handling the necessary radioactive materials could cause severe burns and would likely expose the builders to lethal doses of radiation. Building and transporting such a bomb safely and to avoid detection would likely require so much shielding that it would be “nearly impossible” to move. Weaker dirty bombs made from less radioactive (and more common) materials would be easier to build and deploy, but would have a much smaller physical impact and would likely cause few human casualties.
Attacking a tanker or port facility that handles liquified natural gas (LNG) could create a major explosion, though it's not easy:
To date, no LNG tanker or land-based LNG facility in the world has been attacked by terrorists. However, similar natural gas and oil assets have been favored terror targets internationally. The attack on the Limburg, although an oil tanker, is often cited as an indication of LNG tanker vulnerability.
Former Director of Central Intelligence, James Woolsey, has stated his belief that a terrorist attack on an LNG tanker in U.S. waters would be unlikely because its potential impacts would not be great enough compared to other potential targets. LNG terminal operators which have conducted proprietary assessments of potential terrorist attacks against LNG tankers, have expressed similar views.
If terrorists are looking for human casualties, a ferry is a possible target:
A RAND study in 2006 argued that attacks on passenger ferries in the United States might be highly attractive to terrorists because such attacks are easy to execute, may kill many people, would likely draw significant media attention and could demonstrate a terrorist group’s salience and vibrancy. One U.S. Coast Guard risk analyst reportedly has stated that “in terms of the probability of something happening, the likelihood of it succeeding and the consequences of it occurring, ferries come out at the very high end.” Such attacks have occurred overseas. As noted earlier in this report, terrorists linked to Al Qaeda attacked and sank the Philippine vessel Superferry 14 in 2004.
After examining the details, the report comes to this rather bland conclusion:
It appears, therefore, that while maritime terrorist attacks against the United States may be more difficult to execute and, consequently, less likely to occur than other types of attacks, they remain a significant possibility and warrant continued policy attention.
