• by Mark Walsh  @markfwal, January 24, 2013

Programmatic ad platform AppNexus on Thursday raised $75 million in a fourth-round funding led by Technology Crossover Ventures and including Venrock and Tribeca Venture Partners. That brings its total raised to date to $140.5 million.

The company plans to use the new financing to continue enhancing its technology, introduce new products and expand staff.

“We are going to hire hundreds of engineers over the coming years to build the next generation of our platform …We have some fantastic features coming out over the next couple of months and have an aggressive road map for the rest of the year,” wrote CEO Brian O’Kelley in a blog post today.

He added the company was also investing heavily to keep its system free of piracy, fraud, porn and malicious toolbars, while working on tools to provide more transparency on ad transactions.

In the last year, the company said it has almost tripled revenue and doubled headcount to 400, with new offices in Paris, Hamburg and Toronto. It has also brought on new clients including Interactive Media, Orange and the Canadian Audience Exchange.

The additional business helped AppNexus increase the volume of ad spend handled through its real-time bidding platform to about $700 million in 2012. That translates into processing up to 1 million ad requests per second and serving more than 13 billion ads to Web sites each day.

To help accelerate its growth, the company in November hired former top AOL ad executive Lynda Clarizio as EVP, corporate development and operations. In that role, she oversees corporate and business development as well as administrative operations including people, legal and policy affairs.

In connection with the new funding, David Yuan, a general partner at Technology Crossover Ventures, has joined the AppNexus board of directors.