YouTube is serving notice on video fraudsters: The site said it has started to methodically audit the views a video has received to strip out obviously fake activity, in step aimed at building credibility with advertisers.

Starting this week, YouTube will periodically validate a video’s view count, removing fraudulent views “as new evidence comes to light,” Philipp Pfeiffenberger, a Google software engineer, wrote in a blog post. The change is expected to affect only a “minuscule fraction of videos on YouTube,” he wrote, “but we believe it’s crucial to improving the accuracy of view counts and maintaining the trust of our fans and creators.”

“When some bad actors try to game the system by artificially inflating view counts, they’re not just misleading fans about the popularity of a video, they’re undermining one of YouTube’s most important and unique qualities,” Pfeiffenberger wrote.

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There’s also money at stake: YouTube’s focus on eliminating fake views is a key part of the website’s ongoing efforts to win more business from major brands, said Pivotal Research analyst Brian Wieser. Big advertisers have become increasingly aware of fraud around online video and digital display advertising more generally, he said.

“It’s increasingly table stakes to be able to make claims about aggressively eliminating fraudulent views,” Wieser said.

In 2013, about 11% of Internet video ad sales — amounting to $380 million annually — were fraudulent views generated by botnets or “fake pre-rolls,” which are ads that auto-play without a user selecting a video, according to TubeMogul, a video-ad buying platform.

The new policy goes into action as Google is shaking up the YouTube leadership team: senior VP of ads and commerce Susan Wojcicki will replace Salar Kamangar as the division’s chief, Google announced Wednesday.

YouTube is far and away the biggest Internet video site, with more than 1 billion unique users monthly worldwide watching more than 6 billion hours of video in aggregate. But while it shovels out the most video, YouTube doesn’t sell the most ads in the Internet video biz: In December 2013, Google sites served 353 million ad minutes via 3.6 billion total ads, trailing leader AOL (together with Adap.tv), which delivered 1.85 billion ad minutes via 4.3 billion ads, according to research firm comScore.

Pfeiffenberger also urged YouTube creators to be “extra careful” about working with third-party marketing firms, some of which attempt to drive up views artificially.