Product reviews are an important part of e-commerce, helping consumers make informed choices. But Indians are increasingly distrustful of them.

And one of the reasons they are losing their credibility is the flood of disinformation and tampering of feedback by websites and sellers, according to community-based social network LocalCircles. A survey of over 19,000 people by the network showed 56% saying they don’t trust written reviews, while a substantial 65% don’t trust product ratings.

“Many consumers rely on reviews from other users to decide if the product is fit to be bought or not. Tampering with these reviews leading to a purchase, hence, is nothing less than trying to cheat them,” the Noida-headquartered company said in a statement.

Often, the deceit comes to light after customers have taken delivery of the product. Nearly two-thirds of the respondents experienced a significant variation between a product review and the product.

For some, the distrust stems from first-hand experiences of online retailers refraining from publishing the bad reviews their products receive: 34% of over 4,000 consumers said their unfavourable reviews were not posted on websites. Meanwhile, more than seven in 10 consumers believe fake product reviews have become a norm in e-commerce. But such fears may not be unfounded.

Shilling, that is, pretending to be impartial with an endorsement, is now a business in itself. Sites like fiverr.com, an online marketplace to hire people for paid services, have listings of people who will write favourable reviews for your products or negative ones for your competitor’s – all for a small fee.

“…many businesses are thriving on their ability to provide fake ‘good reviews’,” LocalCircles said. Often, the seller himself rates and reviews his product. “It is also very common for them [sellers] to ask family and friends to rate and review their product. Some even go to the extent of making a purchase from their own business so as to get a ‘verified purchase’ rating and review for their product.”

Keeping all types of reviews up is essential to staying unbiased and building credibility. “We are very protective of our customer voice and go to great lengths to keep reviews up on the site, even if they are aggressively critical or obviously untrue,” an Amazon spokesperson told Indian Online Seller, a website that focuses on small businesses. “This is essential in order to maintain trust in the authenticity of our reviews as a whole. We let other customers weigh in by voting or commenting.”

Some e-commerce players actually go after fraudulent reviews. At most companies, vetting comments is a combined human-machine effort. The founder of MouthShut.com, one of India’s first online review sites, told NDTV that the site detects fraudulent activity by studying the IP address of the user, the frequency and timing of posts, location, and checking for potential astroturfing (when biased sources like employees themselves post reviews). Flipkart and food discovery portal Zomato, too, analyse patterns in origin and behaviour of reviewers using spam-control algorithms and human intervention, NDTV reported.

A possible workaround for customers is to go for products with hundreds of reviews – basically a number that is perhaps too big to allow manipulation by the seller, LocalCircles recommends. And flattering or not, e-commerce sites should make it mandatory to publish all verified purchase reviews. At a higher level, LocalCircles says the government’s department of consumer affairs should monitor such activities.

This article first appeared on Quartz.