The phone tapping was uncovered during investigations into a separate co-location scam. The ED in Delhi arrested Narain on Tuesday, the first time he has been arrested since the irregularities at NSE became a subject of investigation five years ago.
The phone tapping case pertains to Sanjay Pandey, a former Mumbai police commissioner, and some former NSE executives who allegedly monitored calls made by employees between 2009 and 2017 in violation of the law.
In July, Pandey and Chitra Ramkrishna, former NSE chief, were also arrested in the phone tapping case. Ramkrishna was first arrested by the Central Bureau of Investigation in March in the co-location case. Pandey and Ramkrishna are still in custody.
Incorporated by Pandey in 2001, iSec Services was among many IT firms that conducted security audits at NSE between 2010 and 2015, when the alleged co-location scam took place. The investigative agencies have been looking into the role of the security auditor as it should have been able to detect breaches in the NSE system when the scam occurred.