Twitter's made another big buy, its second in the past week.

On Monday, TechCrunch reported that the microblogging site will acquire Dasient, a security startup that offers malware protection for businesses.

A post on the Dasient blog confirms the purchase, which is "effective immediately." The company's staff will work exclusively on Twitter's revenue engineering team and will no longer service new clients.

Founded in 2008 by Neil Daswani, Ameet Ranadive and Shariq Rizvi, the company has been "solving web-scale security problems involving malware and other types of online abuse," according to the company blog post.

"In 2010, Dasient launched the industry’s first anti-malvertising service to protect ad networks and publishers from the scourge of malicious ads," the post went on to explain. "Over the last year, we have been very active in securing the ads and content of the some of the industry’s largest ad networks and web sites."

It is exactly this kind of ad security that caught Twitter's eye. As the popular social network ramps up its monetization effort with new advertising strategies, it will need additional security to weed out malicious advertisers who may pay for their content to infiltrate Twitter's network.

A Twitter rep emailed the following statement to The Huffington Post:

Neil Daswani, Shariq Rizvi and Ameet Ranadive have created technology that provides network security and malware prevention service for some of the largest ad networks in the world. Their team has an excellent understanding of advertising platform-related security issues and will be a valuable addition to the revenue engineering team.

According to TechCrunch, citing unnamed sources, the purchase of Dasient was a big buy "in terms of sheer size of the team."

PCMag points out that Twitter purchased Whisper Systems, specializing in mobile security, in November 2011.

Last week, Twitter acquired social news aggregation startup Summify, folded its staff into the Twitter Growth team and shuttered the smaller company.