Exchange surveillance mechanisms: GSM and ASM

Exchange surveillance mechanisms are systematic processes employed by stock exchanges to monitor trading activity for any irregularities, manipulation, or insider trading. The primary goal is to protect market integrity, ensure fair price discovery, and safeguard investor interests as mandated by SEBI.

Two distinct approaches are used: the Gross Surveillance Mechanism (GSM), which relies on manual review of aggregated data, and the Automated Surveillance Mechanism (ASM), which uses algorithms and real‑time analytics. Both mechanisms operate under the same regulatory umbrella but differ in speed, technology, and human involvement.

For the NISM exam, candidates must recognise which surveillance tool is being referred to in a question, understand its operational workflow, and know the compliance obligations of the exchange and market participants.

• GSM – manual, periodic, broader data sets.
• ASM – automated, real‑time, rule‑based alerts.

The Gross Surveillance Mechanism is a traditional, largely manual process where the exchange’s surveillance team reviews aggregated trade data, order books, and price movements over a defined period, typically daily or weekly. Analysts examine patterns such as large block trades, unusual price spikes, and repeated order cancellations.

SEBI’s Circular on "Market Surveillance" (issued in 2020) requires exchanges to maintain a GSM framework that captures all trades, irrespective of size, and to generate periodic reports for the regulator. The GSM is especially useful for detecting complex schemes that may span multiple days, such as layered spoofing or coordinated wash trades.

Exam relevance: Questions often ask which mechanism would flag a manipulation that unfolds over several days. Remember that GSM’s strength lies in its comprehensive coverage, albeit with a lag in detection.

• Data scope – entire market, all securities.
• Review frequency – end‑of‑day or weekly.

ASM leverages advanced analytics, machine learning, and rule‑based engines to scan live market feeds in real time. It flags anomalies such as price movements beyond predefined thresholds, abnormal order‑to‑trade ratios, and rapid order modifications.

SEBI’s guidelines mandate that exchanges deploy ASM to achieve a detection latency of less than five minutes for high‑risk securities. The system generates alerts that are instantly routed to the surveillance team for further investigation, enabling swift remedial action.

For exam preparation, focus on the speed advantage of ASM and the typical parameters (price volatility, order‑cancellation rate) that trigger alerts. Questions may present a scenario where a price jump occurs within minutes – ASM, not GSM, would be the correct answer.

• Technology – algorithms, AI, real‑time data feeds.
• Alert latency – typically under 5 minutes.

SEBI, through its Market Surveillance Regulations, obliges every recognised exchange to maintain both GSM and ASM. The regulator conducts periodic audits to verify that the exchange’s surveillance architecture meets the prescribed standards for data retention, alert generation, and reporting.

Exchanges must submit daily surveillance summaries, including the number of alerts generated, actions taken, and any escalations to SEBI. Failure to comply can result in penalties, suspension of trading privileges, or revocation of recognition.

From an exam standpoint, remember the dual‑obligation: an exchange cannot rely solely on ASM; GSM is mandatory for comprehensive coverage. Questions may ask which component of the regulatory framework ensures "historical" analysis – the answer is GSM.

• Key documents – SEBI Circular on Market Surveillance (2020), Exchange‑specific surveillance manuals.
• Compliance timeline – daily reporting for ASM alerts, weekly/monthly for GSM summaries.

Surveillance teams monitor several quantitative metrics to identify abnormal behaviour. The most common include:

• Price Volatility Index – measures deviation from moving averages.
• Order‑to‑Trade Ratio (OTR) – high OTR may indicate spoofing.
• Trade‑size Distribution – unusually large blocks relative to average daily volume.
• Bid‑Ask Spread Anomalies – sudden widening can signal manipulation.

Understanding these metrics helps analysts interpret surveillance alerts and provide informed commentary in research reports. In the exam, you may be asked to match a metric with its typical manipulation type.

Remember that the thresholds for these metrics are set by the exchange’s risk parameters and can vary across securities.

Research analysts rely on surveillance outputs to assess the credibility of price movements and to flag potential red‑flags in their coverage universe. When an ASM alert is triggered for a stock in the analyst’s watchlist, the analyst must investigate the underlying cause before issuing a recommendation.

GSM reports are useful for post‑event analysis. Analysts can cite GSM findings in their reports to demonstrate due diligence, especially when explaining abnormal returns in historical performance tables.

Exam tip: Questions may ask how an analyst should respond to an ASM alert versus a GSM report. The correct answer highlights immediate investigation for ASM and retrospective validation for GSM.

• Action on ASM – quick verification, possible trade recommendation pause.
• Action on GSM – detailed analysis, inclusion in research commentary.

One frequent mistake is assuming that ASM alone can detect all forms of market abuse. While ASM excels at real‑time anomalies, it may miss multi‑day collusion that GSM captures.

Another trap is confusing the reporting frequency. GSM reports are periodic (daily/weekly), whereas ASM alerts are generated instantly. Remember the distinction when a question asks about "daily surveillance summary".

Students also forget the regulatory requirement that both mechanisms must coexist. Selecting only one mechanism as "mandatory" leads to a loss of marks.

Finally, avoid mixing up metric definitions – the Order‑to‑Trade Ratio is orders cancelled divided by executed trades, not the other way round.