Almost every latency arbitrage account goes the same way. The first weeks look great: fills are clean, trades last a few seconds, and the equity curve climbs at a steady angle. Then, with no email and no warning, things change. Fills start slipping by half a pip, and always against you. Orders that used to fill in 40 ms now take 300 ms. Spreads on the account look a little wider than the broker’s published ones. A few weeks later compliance writes to say a “trading activity review” is under way.
None of that is bad luck. It is a detection system doing its job. This guide explains how brokers detect latency arbitrage from the trader’s side of the screen: which numbers the risk team actually computes, why arbitrage flow stands out so clearly in them, the usual escalation ladder after an account is flagged, and how to read your own trade log to see whether it has already happened to you.
If you are new to the strategy itself, start with our explanation of how latency arbitrage works. This article assumes you know the basic idea: trading a slow quote against a faster reference feed.
Why brokers look for latency arbitrage in the first place
Detection follows the money. A broker that hedges every trade with a liquidity provider (a pure A-book) is mostly indifferent to your strategy, though its LP may not be, because the LP ends up holding the stale-price loss. A broker that takes the other side of client trades (B-book, or hybrid) books every arbitrage profit as its own loss. One fast account can wipe out the spread income from hundreds of ordinary clients.
So the question a risk team asks is not really “is this arbitrage?” but “is this flow toxic to my book?” Toxic flow means trades that consistently know where the price is going next. Latency arbitrage is the cleanest example of it, which is why it is so easy to measure. For the routing side of this story, see our breakdown of A-book vs B-book brokers.
The single most important metric: markout
If a broker’s risk team could look at only one number, it would be markout: how far the market moves in your favour in the short window after each fill. The broker takes the mid price at the moment of your fill, then again 100 ms, 500 ms, 1 s and 5 s later, and averages the difference across all your trades.
For an ordinary retail client that average sits near zero, or below it once spread is included. Retail traders are, on average, not able to predict the next second of price action. A latency arbitrage account looks completely different. Its trades exist because the price is about to move, so the markout curve jumps up almost at once and then flattens. That shape is very hard to produce by accident.
Markout is powerful because it ignores your story. It does not care whether you call your system a scalper, a news trader or a grid. It measures only whether your fills are systematically ahead of the price, and that is precisely the edge latency arbitrage relies on.
The other signals risk engines combine
Markout alone can throw false positives. A skilled news trader will sometimes produce a positive markout too. So modern risk tools combine it with a handful of behavioural features. None of these proves arbitrage on its own. Together they make a very confident score.
| Signal | O que mede | Why arbitrage stands out | What you’d see in your own log |
|---|---|---|---|
| Markout | Price move in your favour 0.1-5 s after the fill | Trades are opened because the move is already under way | Most trades are in profit within a second |
| Hold-time distribution | How long positions stay open | Tight cluster of seconds, not a spread of minutes to days | Median hold time in single-digit seconds |
| Win rate by hold time | Win rate on very short trades specifically | Short trades are normally a coin flip minus the spread; arbitrage wins most of them | High win rate concentrated on the fastest trades |
| Order timing vs ticks | Delay between a price update on a reference market and your order | Orders arrive in a narrow window right after external moves, before the broker’s own quote catches up | Entries bunched around fast moves and news spikes |
| Slippage asymmetry | Ratio of positive to negative slippage | Once an account is flagged, the broker controls this ratio, so it’s also an outcome | Positive slippage disappears, negative slippage grows |
| Sizing and pattern regularity | Repeated lot sizes, symbols, session times | Bots repeat themselves; humans drift | Same lot on nearly every trade, same few symbols |
| Cross-account links | Shared IPs, devices, mirrored or opposite P&L | Two-leg and multi-account set-ups leave correlated footprints | Not visible to you, but it is checked |
From rules to models
Early detection was a set of hard rules: “flag any account with an average hold time under N seconds and a win rate over X%.” Rules like that are easy to step around and they catch plenty of innocent scalpers. Most serious brokers and their technology vendors now feed the features above into a scoring model that ranks accounts by toxicity, often refreshed daily or even intraday. The practical effect is that no single threshold exists to stay under. The model weighs the whole profile, and the profile of a pure latency strategy is distinctive.
What happens after an account is flagged
Brokers rarely close an account the moment it is flagged. Closing is the loudest option and it ends the spread income too. What usually happens is a quiet escalation, each step designed to take the edge away while the account keeps trading. Knowing the ladder matters, because each rung leaves a visible trace in your results.
Step 2: execution changes
The account is moved to a different execution group. Orders may be held for a short delay before they are filled. A delay of even a hundred milliseconds is enough to erase an edge that lives in the first few hundred. Slippage becomes one-way: when the price moves against you during the delay you get the worse price, and when it moves for you the order is filled at the requested price or rejected. This is what a “virtual dealer” set-up does, and it is the most common response by far.
Step 3: pricing changes
Next the account may get a wider spread markup than the published one, a slower or smoothed price feed, or a last-look window in which the broker or its LP can reject fills that have become unprofitable for them. On paper your strategy still “works”; in practice the expected value per trade falls to around zero.
Step 4: account action
Finally comes the visible step: a trading review, reduced leverage, a block on certain instruments, a closed account, or, in the worst case, cancelled profits under an “abusive trading” or “price latency exploitation” clause in the client agreement. Read that clause before you deposit, because it decides whether a dispute is even worth having.
How to tell if your account has already been flagged
Brokers don’t announce steps 1 to 3, but you can measure them. You have the same data they do for your own trades. Run this check every week:
- Compare execution time over time. Export order-sent and order-filled timestamps. If your median fill time jumps from tens of milliseconds to hundreds, and the jump is not explained by your VPS or network, the account was most likely moved.
- Count positive versus negative slippage. On a fair account both happen. If positive slippage drops to almost nothing while negative slippage grows, the execution is asymmetric.
- Track profit per trade, not just win rate. A falling average profit with an unchanged signal count means the edge is being taxed somewhere between your order and the fill.
- Watch the reject and requote rate. A sudden rise in “off quotes” or “price changed” errors on fast moves is the classic last-look footprint.
- Compare the account’s spread to the published spread. Log the bid/ask at entry. A persistent extra fraction of a pip is a markup, not market conditions.
Any one of these can be noise. Two or three together, starting in the same week, are a strong sign that the account has climbed the ladder. The rational move then is usually not to fight the broker but to withdraw and redeploy.
What this means for anyone running arbitrage
Detection is not a reason to give up on latency arbitrage. It is a reason to run it as a professional operation and not a lottery ticket. In practice that means:
- Pick the venue first. The detection model matters less when the broker’s business model does not suffer from your profit. Our guide on como escolher uma corretora para arbitragem covers what to check: execution model, LP set-up and the wording of the client agreement.
- Read the terms, literally. If the agreement explicitly bans exploiting price latency, you are on borrowed time there, however good the first month looks.
- Withdraw often. Profits sitting in an account are the profits that can be reviewed. Regular withdrawals limit what a late-stage review can touch.
- Keep your own logs. Timestamps, prices and slippage per trade are your evidence in any dispute, and they are also your early-warning system.
- Expect a lifecycle. Plan for an account to have a useful life measured in weeks or months, and size your effort accordingly.
Traders who want to understand the counter-measures that strategy developers have built in response to these models (trade-pattern variation, multi-account exposure rotation and similar techniques) will find them covered in our article on a nova geração de tecnologia de negociação de arbitragem. Whatever approach you take, the broker’s own terms remain the rulebook that applies to your account.
Perguntas frequentes
Is latency arbitrage illegal if the broker can detect it?
Detection and legality are different questions. In most jurisdictions trading on a broker’s slow quote is not a criminal matter. It is a contractual one, governed by the broker’s client agreement. We cover the legal side in detail in is forex arbitrage legal?
How long does it take a broker to detect latency arbitrage?
It depends on trade volume and how sophisticated the broker’s tooling is. Markout and hold-time statistics need a sample of trades to become reliable, so an active account at a broker with modern risk software can be scored within days. At a smaller broker that reviews accounts manually it can take weeks.
Can a broker cancel my profits after detecting arbitrage?
Some client agreements give the broker the right to cancel trades or profits judged to come from price latency or “abusive” trading. Whether that holds up depends on the exact wording and on the regulator. That is why reading the agreement before depositing, and withdrawing regularly, matter so much.
Will a fast VPS or low latency alone get my account flagged?
No. Low latency by itself is not a signal. Brokers want fast clients who trade normally. What gets an account flagged is what the speed is used for: consistently positive markout, very short hold times and high win rates on those short trades.
Do brokers share information about arbitrage traders?
Brokers that use the same white-label technology, bridge or liquidity provider can end up with similar views of toxic flow, and LPs see flow from many brokers. Don’t assume a new account at a related broker starts from a clean slate.
Is every account with slippage a flagged account?
No. Slippage is normal in fast markets. The warning sign is a sudden change in the pattern: slippage becoming almost entirely negative, together with slower fills and more rejects, starting at roughly the same time.
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