The National Investigation Agency (NIA) in India was established in 2009 to investigate and prevent terrorist activities and other crimes against the country's security. Here are some of the ways in which the NIA helps maintain national security:

• The NIA has the authority to take up cases related to terrorism and other offenses against the security of the country under several laws such as the Unlawful Activities Prevention Act (UAPA).
• It has a specific focus on the investigation of transnational and international crimes that threaten the unity, integrity, and sovereignty of the country and works closely with other agencies such as the Intelligence Bureau and RAW.
• The NIA has the power to investigate and prosecute cases across multiple states, which helps in the efficient handling of cases with a wider reach.
• The agency has the expertise and technology to collect and analyze data from various sources, including social media, to identify and monitor suspects and potential terrorist activities.
• The NIA's proactive action and swift response in several cases has helped prevent many terrorist attacks in the country, thereby preserving national security.

Overall, the NIA is a vital component of India's national security machinery that helps prevent and combat terrorism and other crimes that pose a threat to its citizens and sovereignty.