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FollowingACDC report reveals "killer whale" accounts on Polymarket: Small bets and high winning rates raise concerns about insider trading
A new report released by the Anti-Corruption Data Collective (ACDC) identified 556 Polymarket accounts and called them "killer whale". These accounts focus on making small, precise bets on low-odds events, with a win rate of over 75%.
What did ACDC find?
The Anti-Corruption Data Collective released a report titled "Classifying Insider Trading Risks", which analyzed 78,496 unpopular bets placed in 12,355 wallets on Polymarket. ACDC defines an unpopular bet as a single bet with an amount of more than $2500 and an odds of 35 cents or less (i.e., the probability of an event occurring does not exceed 35%).
The researchers divided four groups from these data: killer whales, whales, robots and "small fish." The report shows that 556 "killer whale" wallets only bet on a few markets and topics, but their winning rate is extremely high, exceeding 75%.
(Photo source: ACDC. The chart shows the winning odds of unpopular bets by different categories of bettors.)
There are 3,278 "whale" accounts, which conduct large transactions in multiple markets;760 "robot" accounts are at least partially automated; and the remaining 7,761 accounts are "small fish".
In an early report in April, the ACDC found that the winning probability of unpopular bets was just 14% across the Polymarket platform, but rose to 25% in the political market and 52% in the military and defense markets. Report authors Michele Kendler-Creech and David Sacconi calculated that winning and unpopular bets in the military market alone brought in $9.3 million in gains.
Why is insider trading on Polymarket a national security issue?
ACDC found that when placing bets on major military events, the "killer whale" account always takes the lead, followed by "whale" and "robot". This is no different from experienced traders observing public blockchains and imitating insider trading behavior in real time. Although this kind of "follow-up trading" is legal, it may expose insider activities to the public.
For example, when a certain "killer whale" made a bet a few hours before the US military launched an attack on Iran in June 2025, a "robot" and a "whale" followed suit and bet $200,000 and $100,000 respectively. This kind of blockchain transparency, which allows follow-on transactions, would also allow foreign militaries and intelligence agencies to act on market signals.
It is difficult to trace the true identity behind the orca accounts because the funds flow under false names and must be subpoenas to obtain information from exchanges that hold funds for thousands of customers. The ACDC concluded that the only solution was to ban the highest risk market categories completely.
There have been many insider trading incidents on the prediction platform. In April, the U.S. Department of Justice charged a U.S. soldier named Cannon Ken Van Dyke, accusing him of using confidential details of the capture of Nicolas Maduro to bet about $33,034 on Venezuelan contracts and subsequently made a profit of about $409,881. In May, federal prosecutors for the Southern District of New York sued Google engineer Michelle Spanuolo, accusing him of using internal company data to win $1.2 million on Polymarket. In addition, Bubblemaps recently stated on CBS's "60 Minutes" program that it has tracked nine associated accounts that have won a total of more than $2.4 million in more than 80 Iran war bets, with a win rate of 98%. "Luck alone cannot explain these numbers," noted Nikolai Viman, CEO of Bubblemaps.
