Prediction markets let people wager on just about anything — from basketball games to elections. And among more jarring bets recently, the fate of the U.S. and Israel’s war against Iran.

Shortly ahead of a fragile ceasefire agreement earlier this week, a new group of accounts on prediction market platform Polymarket made highly specific, well-timed trades betting there’d be an announcement about a halt in fighting for April 7. Some quickly pocketed awards, which amounted to hundreds of thousands of dollars in profits combined. Others are still awaiting payouts as an end to the deadly conflict still seems uncertain.

Regardless, the trades once again put the spotlight on a murky — and growing — world of speculative, 24/7 transactions now filling the internet. And some have raised questions about suspicious activity, including an anonymous Polymarket trader pocketing more than $400,000 following the U.S. military’s capture of former Venezuelan President Nicolás Maduro in January.

The timing and subjects of such trades have fueled concerns about potential insider trading — with calls increasing among lawmakers for investigations. Popular platforms, including Polymarket, have rolled out added guardrails in efforts to combat insider trading recently, but critics say it isn’t enough.

Meanwhile, because prediction market wagers are categorized differently than traditional forms of gambling, tensions about government oversight have erupted. President Donald Trump’s administration has already thrown its support behind company operators — and sued three states over their efforts to regulate them further.

The scope of topics involved in prediction markets can range immensely. Recently, there’s been a surge of wages on elections and sports games. But some users have also bet millions on things like a rumored — and ultimately unrealized — “secret finale” for the Netflix’s “Stranger Things,” whether the U.S. government will confirm the existence of extraterrestrial life and how much billionaire Elon Musk might post on social media this month.

In industry-speak, what someone buys or sells in a prediction market is called an “event contract.” They’re typically advertised as “yes” or “no” wagers. And the price of one fluctuates between $0 and $1, reflecting what traders are collectively willing to pay based on a 0% to 100% chance of whether they think an event will occur.

The more likely traders think an event will occur, the more expensive that contract will become. And as those odds change over time, users can cash out early to make incremental profits, or try to avoid higher losses on what they’ve already invested.

Proponents of prediction markets argue putting money on the line leads to better forecasts and allow you to gauge public opinion as an alternative to polling. And some think there’s value in monitoring prediction markets for potential news, particularly elections.

Still, prediction markets can also be wrong. People investing their money may be closely following certain events, but others could just be randomly guessing.

Who is behind all of the trading is also pretty unclear.

The companies running today’s biggest platforms know who their customers are — as they collect personal information to verify identities and payments. But most users can trade under anonymous pseudonyms on public-facing websites, making it difficult for the world to tell who is profiting off many event contracts.

Critics also stress that the ease and speed of joining these 24/7 wagers leads to financial losses everyday, particularly harming users who may already struggle with gambling.