As real estate websites grapple with data scrapers, a firm that’s dedicated to battling “bad bots” — sometimes on the behalf of multiple listing services (MLSs) — has filled its war chest with an additional $21 million. Distil Network Inc.’s cloud-based, automated “bot blocking solution” acts as a shield between a website and end users, identifying “bad bots” (programs that scrape data) and only letting through legitimate traffic, including “good bots” like search engines. In 2013, the firm launched what it hoped would be an “industrywide intelligence network” to identify and thwart those who scrape real estate listing data without permission. At the time, Distil said it had found that up to 60 percent of Web traffic on public-facing MLS websites comes from da…