You're not wrong on this. There are, and it is. One of my previous jobs I worked at a dark pool exchange. A dark pool is an entirely legitimate and regulated quasi off the books market. It's "dark" in that prices at the exchange are not listed; no best bid/offer or any other order information is advertised. It's also members (customers) only. It's not available to the general public. It's primarily a ways of moving high volumes of trades with the intention of not moving the market. Executed trades are reported as required, and NMS (National Market System) Regulations have to be abided by. i.e. A dark pool cannot trade outside of the NBBO (National Best Bid/Offer) without first having taken (bought /sold) top of the book at the NMS exchanges that have the NBBO. We're still subject to SEC, FINRA reporting and regulation and are regulated by the same.

It was a small firm, less than 10 engineers working on the technology stack, so we all wore many hats. Besides working on the trading system, I was also responsible for working with our chief compliance officer to gather trade data for inquiries from SEC, FINRA, even the FBI. Most of what they were looking for was not insider trading, but other prohibited activities such as spoofing and front running.

I've also worked at hedge funds, private equity funds, mutual funds & investment advisors. Every firm I've worked for (especially the hedge funds & PE funds) have used technology to their best (legal) advantage they can. Need lower latency? Co-location at the exchange is a perfectly legal option. Racks closer to the exchanges offer a premium rent over those farther away. Microwave transmission for line of sight? Most certainly. Lower latency, but also significantly lower bandwidth. Bonus points for being able to bounce a signal off the ionosphere from Chicago to London faster than satellite or sea cable.

That said, when it comes to Congress, they're in the unique position of not just being privy to an absurd amount of material nonpublic information that unscrupulous actors can make a killing off of, they're also in the unique position of enacting (or retracting) laws that affect the companies they're trading on. It's this power that is unique to Congress, and why they deserve extra attention and rules on reporting, holding periods, trading windows, etc.

Insider trading is a problem among the general public, but it's not nearly as big of a problem as the media makes it out to be. Yes, there are unscrupulous firms out there, but the vast majority take the rules and regulations seriously, because you have to, or you will no longer be in business and real jail time for potential violations. I believe Congress should be held to a higher standard than the general public because of their unique power over the industry.