In an effort to combat the intentional adulteration of food, FDA on Thursday finalized the last of seven major rules under the FDA Food Safety Modernization Act (FSMA).

For the first time, U.S. and domestic foreign food facilities must complete and maintain a written food defense plan to examine potential exposure to intentional contamination of food aimed at causing wide-scale harm to public health, the agency said in a news release.

FDA cautioned that such intentional “acts are unlikely to occur."

Under the new rule, which was proposed in December 2013, facilities must identify and implement strategies to mitigate vulnerabilities to intentional adulteration and develop food defense monitoring procedures and corrective actions, FDA said. Facilities also must confirm the food defense system is working and verify personnel receive proper training and maintain records, the agency noted.

The new rule covers 3,400 firms that operate 9,800 food facilities, and depending on the size of their business, food manufacturers have three to five years to comply. Smaller companies are exempt.

“Today’s final rule on intentional adulteration will further strengthen the safety of an increasingly global and complex food supply," said Stephen Ostroff, M.D., FDA’s incoming deputy commissioner for foods and veterinary medicine, in a statement. “The rule will work in concert with other components of FSMA by preventing food safety problems before they occur."

The six other major rules adopted by FDA under FSMA relate to preventative controls for animal and human foods, produce safety, importer verification to ensure food meets U.S. safety standards, a voluntary program for the accreditation of third-party certification bodies, and sanitary transportation of animal and human foods.

“While acts of intentional adulteration may [take] many other forms, including acts of disgruntled employees or economically motivated adulteration, the goal of this rule is to prevent acts intended to cause wide-scale harm," FDA noted in a fact sheet on the intentional adulteration rule. “Economic adulteration is addressed in the final preventive controls rules for human and animal foods."