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Some ad-tech companies have severed ties with Newsweek Media Group (NMG) amid allegations that several of NMG’s websites have pedaled fraudulent traffic, The Wall Street Journal reports.

The companies — AppNexus and SpotX — ended their relationship with NMG as DoubleVerify, a digital media measurement company, flagged four NMG-owned websites for hosting a piece of code that inflated the performance of sites’ ads.

Fraudulent traffic allegations could discourage other brands from advertising on the company’s sites. The findings signal that Newsweek and IBT have risky ad inventory, and brands could be wasting ad spend by running campaigns on NMG’s properties. Mounting ad fraud concerns bode ill for the overall image of NMG, which is already facing a separate investigation led by the Manhattan district attorney's office for suspected bank fraud.

Newsweek’s ad-tech woes highlight the industry-wide issue of ad fraud:

Other publishers are also struggling with ad fraud. In September 2017, the Financial Times found 25 ad exchanges selling inventory purporting to be FT.com's, for example. Moreover, in January, News UK found 2.9 million bids were made on inventory disguised as News UK’s The Sun and The Times of London brands, according to Digiday.

In September 2017, the Financial Times found 25 ad exchanges selling inventory purporting to be FT.com's, for example. Moreover, in January, News UK found 2.9 million bids were made on inventory disguised as News UK’s The Sun and The Times of London brands, according to Digiday. And this is contributing to significant wasted ad spend. In 2017, advertisers globally were projected to waste $6.5 billion due to fraud. Moreover, News UK estimates marketers are wasting $950,000 per month on fake inventory. For context, global digital ad spend reached an estimated $209 billion in 2017.

Advertisers can mitigate wasted ad spend by purchasing inventory from private marketplaces (PMPs). PMPs are invite-only auction environments where high-quality publishers offer their ad inventory to a select group of ad buyers. PMPs are akin to direct sales, so there's virtually no risk in this method of ad buying. Brands are beginning to embrace PMPs — SpotX announced in early 2017 that PMP deals accounted for about 45% of ad spend on its platform, for example.