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Comment by getcrunk | Hacker News Reader

Wouldn’t they block/suspend the account/credentials?

The product was for end users so the traffic was coming from any account. They never discovered the accounts we used for testing. At least, the American ones didn't. When we finished with US companies, we went for Singapore.

Our CEO was friendly with an investor who had an account at some big Singaporean trading firm called Lim Tan. He gave us his account credentials and I began working. A few days later my boss comes over to my desk and says "stop whatever you're doing right now." Apparently my traffic had set off so many alarm bells that the CTO of Lim Tan was woken up at 2am. They permanently banned the investor, which I felt really bad about. What's crazy is that I wasn't even doing anything weird. I was just poking a bit at their authentication methods. That was when I learned that Singapore tech doesn't fuck around.

I wonder if using something like puppeteer or playwright to actually make the server think everything is being done client-side would still raise flags.

Scraping a well-built API at human speed often isn't terribly useful, and once you start ramping up the scraping, it's account creation/patterns/use frequency that will set an alarm.

Faking real user clients won't prevent these alarms.

The purpose of our work wasn’t scraping - we were building a unified UI where our users could trade with any vendor of their choosing. Kinda like Plaid but specifically for retail stock trading. So the goal was to implement their trading API.

You can just.. do that? I think I discovered why all my ideas suck.

Yep. Though it’s really hard. To capture the US market (E*Trade, Fidelity, TD Ameritrade, Scottrade, Schwab, Interactive Brokers, Robinhood) it took me and another engineer almost 2 years. It’s non-trivial.

Always use puppet accounts for reverse engineering.

Reverse engineering the dudes holding your funds isn't a good idea to begin with. Too much risk. Better to work with them directly or switch to a better service which does feature APIs.

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