Four companies that sell security technology have been granted liability protection from lawsuits triggered by an act of terrorism, the Department of Homeland Security plans to announce today.

The department has worked for more than a year on regulations intended to encourage companies to come forward with innovative technology and services, in part by assuaging fears that they could be held responsible for the consequences of a catastrophic attack.

Among those receiving the limited liability protection is Bethesda-based Lockheed Martin Corp.'s risk assessment platform, the computer system at the heart of the aviation screening program called CAPPS II. It is designed to use public records and intelligence to determine whether an individual poses a security threat. The other companies produce explosive-detection systems, biohazard sensors and devices designed to neutralize explosive devices.

Homeland Security officials consider the liability protection crucial in spurring development of new technologies to protect the nation. The authority comes from a law approved in 2002 called Support Anti-Terrorism by Fostering Effective Technologies (SAFETY) Act, which was included in the legislation that created the department.

"We need to make sure that technologies that protect the American people are deployed," said Penrose "Parney" Albright, the department's assistant secretary for science and technology.

Scores of companies have applied for the designation and certification that provides the legal protection, and a dozen or so more will receive the designation before long, officials said. But the process of applying can take up to 110 hours and require a company to provide pages of details about its operation and financial condition. Approval can take as long as three months, according to a Homeland Security Department document.

Department officials streamlined the process after companies complained last fall about the task of applying for the designation.

Benefits for the makers of "qualified anti-terrorism technologies" include a prohibition on punitive damages, limits on payments to plaintiffs and limits on the amount that a business will pay for liability insurance coverage. The SAFETY Act says businesses should be able to obtain insurance at "prices and terms that will not unreasonably distort the sales price" of their products.