Great question – It's a mixture of data analytics and human intelligence:
We access the data of the company, meaning their funding, the date of funding, open positions, press releases, the niche they are in and further use keyword scrapers to cross polinate which company is likely to look for help.
Example: If a new financial services start–up, that just raised $120 million, stores sensitive user information and they have the words "secure data" on their website and is actively hiring for cybersecurity specialists, they are very likely to be open to a service in the cybersecurity space (and can afford it).
Then, and only then, we include them in our list.