Retired Army Captain Babu was arrested in Vellore, Tamil Nadu, after police received an intelligence tip‑off that he had shared sensitive Defence Research and Development Organisation data with his partner.
Babu, 52, served as a captain in the artillery regiment before retiring in 1994 and later worked for DRDO, making the breach a serious concern for national security.
Investigators say the woman, whose identity and nationality remain unconfirmed, may have used the relationship to gather the information, and they are probing whether it was passed to a foreign intelligence network.
A senior police officer told NDTV that such data cannot be shared, adding that the police have yet to determine if the partner was Pakistani and that they will use WhatsApp IP details to confirm.
Babu was tracked to a hideout near Arani in the Tiruvannamalai district, close to Vellore, and handed over to central investigative agencies for further questioning.
The case will be examined by the central authorities, who plan to scrutinise his communications and digital records to establish the extent of the leak and any foreign links.