Stock Exchange Surveillance
Stock exchange surveillance refers to the real-time and post-trade monitoring systems operated by stock exchanges (BSE and NSE) and SEBI to detect unusual trading patterns, potential market manipulation, insider trading, and abnormal price or volume movements in listed securities.
The integrity of a stock exchange depends fundamentally on fair and transparent price discovery. If certain market participants are able to manipulate prices, front-run others' orders, or trade on material non-public information without detection, the entire framework of investor confidence in the market is undermined. Stock exchange surveillance is the frontline defence against such market integrity violations, employing sophisticated technology and regulatory protocols to identify anomalies in real time and in post-trade analysis.
Both BSE and NSE operate dedicated Market Surveillance Departments that function continuously during market hours and conduct post-trade analysis after market close. These departments use algorithmic surveillance systems that monitor every trade executed on the exchange, scanning for patterns that deviate from established baselines — including unusual spikes in volume relative to the historical average, price movements that are disproportionate to market-wide or sector-wide trends, sudden increases in open interest in derivatives, and trading patterns that suggest wash trading or circular trading.
SEBI's integrated market surveillance system (IMSS) works at a higher level, aggregating data from both exchanges and the depositories to provide a consolidated view of trading activity across the entire market. IMSS enables SEBI to identify patterns that may not be evident at the individual exchange level — for example, an entity that is simultaneously building a large futures position on NSE while accumulating shares in the cash segment on BSE. Cross-market surveillance is essential for detecting sophisticated manipulation strategies that exploit the simultaneous operation of multiple market segments.
Surveillance-triggered actions follow a graduated escalation path. If the exchange's surveillance system detects anomalous trading in a security, the exchange may first issue a surveillance alert to the trading member involved, requesting explanation for the unusual pattern. If the response is unsatisfactory or no response is received, the exchange may impose Graded Surveillance Measure (GSM) or Additional Surveillance Measure (ASM) framework restrictions on the security. Under GSM, trading in the stock may be shifted to a call auction mechanism with periodic matching (rather than continuous trading), reducing the ability of manipulators to make rapid trades. The GSM/ASM framework was introduced by SEBI and the exchanges in 2017 and has been periodically refined.
Referrals to SEBI for formal investigation are made when the exchange's surveillance analysis reveals prima facie evidence of market manipulation, insider trading, or other regulatory violations. SEBI then conducts its own independent investigation, with the power to call for records from intermediaries, summon individuals for examination, and freeze trading accounts during the investigation. Enforcement actions arising from surveillance referrals can include monetary penalties, debarment from the market, disgorgement of unlawful gains, and criminal prosecution in cases involving serious fraud.